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TUCoPS :: Phreaking Technical System Info :: 6_6_01.txt

Q.601 to Q.608 plus annexes





                                FASCICLE VI.6

                        Recommendations Q.601 to Q.699

                      INTERWORKING OF SIGNALLING SYSTEMS

                                  SECTION 1

                            GENERAL CONSIDERATIONS

                             ____________________
                             Recommendation Q.601
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

1 :  GENERAL
~~~~~~~~~~~~
 * 1.1 :  Change from narrative to SDL presentation

   These Recommendations provide a set of interworking specifications for
CCITT signalling systems.  The specifications are based on the CCITT
Specification and Description Language (SDL) described in Recommendations
Z.101 to Z.104.  In these Recommendations on interworking, the SDL is used as
a specification language.

   Existing specifications in narrative form have not completely and
unambiguously specified interworking of CCITT Signalling Systems.  In
addition, the introduction of digital switching, transmission and signalling
systems creates new interworking demands.

   Previous interworking specifications have been analysed and reconsidered in
preparation of the present Recommendations.  Where discrepancies exist between
the previously printed interworking specifications and the interworking
specifications of the present Recommendations, the latter shall be binding.

   The new SDL interworking specifications will not replace the existing
(narrative) specifications of the signalling systems concerned.  They will
only cover that part of the signalling system procedures which is of
importance to interworking.  The detailed procedures of the signalling systems
are to be found in the existing Recommendations (Red Book, Fascicles VI.2,
VI.3, VI.4, VI.7 and VI.8).  Furthermore, only those switching procedures are
shown that are relevant to interworking.

   SDL provides an implementation independent and comprehensive method of
presentation.  It encompasses the previous interworking Recommendations and
ensures that the interworking conditions are included in a regular and
formalized manner.  The chosen method facilitates the specification of
interworking with future signalling systems.  The use of well defined events
with a graphical presentation reduces readers' language problems.



 * 1.2 :  Compatibility between signalling systems

   During the development of CCITT Signalling Systems, the signalling capacity
has constantly been increased.  In this way it has been possible to
incorporate new features.  However, it is not always possible to transfer
these features when interworking with older systems.

   In the case of signalling systems with large signalling capacity, it is
possible to transmit distinct statements on certain conditions, e.g.  "busy",
"type of connection", etc.  On the other hand, however, signalling systems
with small signalling capacity require more general meanings to be assigned to
the signals.  Figure 1/Q.601 illustrates this by an example.



 * 1.3 :  Interworking combinations

   Since the CCITT Signalling Systems are to be used for international
telephone communication, interworking between the different signalling systems
must be ensured.  Interworking takes place in a transit exchange which must
possess suitable equipment for processing the signals of both signalling
systems involved.  Interworking of the signalling systems can take place on
all levels of the telephone network:

   o National,

   o Regional,

   o International.

   With a number of different signalling systems the maximum number of
interworking combinations will be:

                             i  = s  | (mu | s  - 1)


   If the present standardized Signalling Systems No.  4, No.  5, No.  6, No.
7, R1 and R2 only are taken into account, a total of 30 different interworking
combinations is obtained with s = 6.

                                                        Figure 1/Q.601, p.

   The number of possible combinations becomes even greater if the national
signalling systems are taken into account.

   The method for interworking of standardized CCITT Signalling Systems
described in these Recommendations may also be advantageous for interworking
with other signalling systems.


                             ____________________
                             Recommendation Q.602
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
2 :  INTRODUCTION
~~~~~~~~~~~~~~~~~
   Interworking is defined to be:
  
   o The controlled transfer of signalling information across the interface
     between different signalling systems where the significance of the
     transferred information is identical or where the significance is
     translated in a defined number, and

   o The performance of appropriate switching procedures in association with
     the transfer.

   o The duration of interworking commences with the instant when an outgoing
     signalling system is successfully selected and the interworking continues
     throughout the call until the connection is released.  Interworking
     ceases with the release of the connection whether the release is
     initiated by reception of a clear-forward signal or in response to some
     other condition.



 * 2.1 :  Functional partitioning

   When interworking is specified in SDL, three separate functional blocks
with distinct procedures are used (see


                       In the Recommendations on  interworking  of  signalling
                       systems the term "procedure" is used in the same way as
                       the term "process" in Recommendation Z.101, S 2.1

   Figure 2/Q.602), namely

   o The incoming signalling system logic procedures,

   o The interworking logic procedures,

   o The outgoing signalling system logic procedures.

   It is understood that interworking logic procedures are dealt with in the
second functional block.  This functional subdivision allows only those events
which can be processed within the individual incoming and outgoing signalling
system logic procedures part to be sent to or from the interworking logic
procedures part.

   Both the incoming and outgoing signalling system logic procedures cause
actions such as the sending of an acknowledgement signal, the starting of time
supervision, and the generation of an interworking event that includes
additional information, e.g.  the use of satellite circuits and echo
suppressors.

   The action following the reception of an interworking event may be the
generation of one or more signals as well as the operation of internal
signalling and switching procedures.

   The interworking logic procedures are used to specify the action to be
taken in all cases, especially when there is no direct translation from an
interworking event to a signal.



 * 2.2 :  Descriptive tools

   A general approach to specifying interworking - known as events approach -
is used.

   To prepare SDL diagrams three sets of events are used (see Recommendation
Q.603), namely

   o Forward Interworking Telephone Events (FITEs)

   o Backward Interworking Telephone Events (BITEs)

     and

   o Switching Processing Interface Telephone Events (SPITEs).

   FITEs perform information transfer in the forward direction from an
incoming signalling system to an outgoing signalling system.

   BITEs perform information transfer in the backward direction from an
outgoing signalling system to an incoming signalling system.

   SPITEs describe the information flow at the functional interface between
signalling and switching.  These events are considered to be internal to the
signalling procedures.

   In the events approach, all information transfer between any incoming and
outgoing signalling system occurs at a standard interface by means of
interworking telephone events.  This is illustrated in Figure 2/Q.602.  The
concept of an interworking event is generally valid and applies to all
interworking combinations.

   To provide a tool for the interworking specifications, information analysis
tables | see Recommendation Q.604) are prepared.  They identify the
information elements of all forward and backward signals (which are relevant
to interworking) for each signalling system.  They also identify the possible
information loss, addition or change which occurs in the case of interworking
of signalling systems.

                                                        FIGURE 2/Q.602, p.

  * 2.3 :  Symbols

   The symbols and rules of SDL used for interworking specifications are
presented in Recommendation Z.102.



 * 2.4 :  Rules for interworking diagrams

   The general objective is to present all the interworking specifications by
means of SDL.

   The following rules apply to interworking specifications:

2.4.1 The interworking specifications shall be implementation independent.
~~~~~
2.4.2 They shall facilitate the specification of interworking with other
~~~~~ signalling systems.

2.4.3 They shall be unambiguous and as complete as possible, this means
~~~~~ specifically that:

      a) Only those switching procedures shall be represented which directly
         influence the interworking of signalling systems;

      b) Only those procedures of the outgoing and the incoming signalling
         system logic are specified which are relevant to interworking, i.e.
         procedures which are signalling system dependent and others which
         have no influence on the interworking procedures are not represented
         in the functional parts of the outgoing and incoming signalling
         system logic procedures;

      c) Detailed information, such as the exact description of the compelled
         signalling cycle, recognition times of signals, encoding, frequencies
         used, is not described in the outgoing or incoming functional parts.
         Such details can be found in the specifications of the signalling
         system;

      d) Conditions resulting from malfunctions of equipment which have no
         relevance to interworking, shall not be taken into account.

2.4.4 SDL connector symbols are used to cover some detailed procedures that
~~~~~ need not be represented when their descriptions are not important for
the interworking procedures.

2.4.5 Equipment terminology, e.g.  "register" mentioned in the logic
~~~~~ procedures is understood to be functional.

2.4.6 The information analysis tables include only signals relevant to
~~~~~ interworking.  Any internal signals with a meaning specific to a single
signalling system are not listed.

2.4.7 In drawing the SDL diagrams for the interworking specifications, it was
~~~~~ assumed that no time elapses between consecutive states; i.e.  state
transitions are instantaneous.  Time elapses only within a state.


                             ____________________
                             Recommendation Q.603
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
3 :  EVENTS
~~~~~~~~~~~
   All information transfer between incoming and outgoing signalling systems
logic procedures occurs as events.  These events are represented as FITEs,
BITEs and activation signals.  In addition, SPITEs are used internally.

   The translation of the information content of a signal into its
corresponding interworking telephone event must not lead to a change of its
information content, i.e.  the information content must be translated only
into one single interworking telephone event.

   See Annex A to Recommendations Q.601-Q.608.  Tables A-1 to A-3 list all of
the forward interworking telephone events (FITEs), backward interworking
telephone events (BITEs) and switching processing interface telephone events
(SPITEs).

   There are some events which are the direct result of signals received in
some particular call phase.  These events perform the transfer of signalling
information.  However not all signals directly generate interworking events.

   There are some events which are the result of signals in a particular call
phase and internal logic procedures.  This applies particularly to routing,
country code indications and echo-suppressor control.

   There are some events (e.g.  due to time-outs) which are purely the result
of internal interworking logic procedures.  In addition, it may be useful to
consider the internal procedures of the various signalling systems, which do
not generate interworking events.

   In using the events approach the following rules are observed:

   a) In generating events all the circumstances under which the event may
      arise are examined so that the event description is exact.

   b) All events which have been identified by considering the response of a
      signalling system to events are included in Tables A-1 to A-3.


                             ____________________
                             Recommendation Q.604
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
4 :  INFORMATION ANALYSIS TABLES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Information analysis tables are provided for each signalling system.  These
tables list the information elements of the forward and backward signals for
CCITT signalling systems.

   Tables A-4 to A-8 show the forward signals relevant to interworking of
Signalling Systems No.  4, No.  5, No.  6, No.  7, R1 and R2, split up into
their individual information elements.  In these tables, comparisons are made
between the contents of the signals used by the different systems.

   Tables A-9 to A-13 show the backward signals relevant to interworking of
Signalling Systems No.  4, No.  5, No.  6, No.  7, R1 and R2, split up into
their individual information elements.  In the rows headed "corresponds to
signal No.  .  | | of Signalling Sys- tem .  | | " the signals are entered
together with their corresponding signal, if any, in the different systems.

   The tables include an indication to the other signalling systems where:

   o Equivalent signals have the same information content,

   o Equivalent signals are not provided,

   o Equivalent signals contain less or substitute information,

   o Equivalent signals contain additional or changed information.



 * 4.1 :  Information content of the signals

   The individual signals are assigned specific information so as to enable
messages to be transmitted.  The meaning of these signals can be seen from the
specifications of CCITT Signalling Systems.

   With regard to their information content, a basic distinction can be made
between:

   o signals containing a single information element,

     and

   o signals containing several information elements.

   An information element is understood to be the smallest indivisible
component of information (within a signal) considered in this Recommendation.

   For the interworking of different signalling systems, the information
content of the signals to be translated is of great importance.  In the case
where two signalling systems interwork, it is possible to assign all signals
used in the CCITT Signalling Systems to one of the following categories:

   a) signals coinciding in all information elements;

   b) signals coinciding at least in one, but not in all information elements;

   c) signals coinciding in no information element at all.



 * 4.2 :  Consequences

   If signals with identical information content are present in the signalling
systems, the interworking condition is fulfilled.  No modification of
information occurs (refer to a) of S 4.1 above).

   If the signal meanings do not agree in all information elements, those
signals must be allocated to one another where maximum agreement is to be
achieved, so as to minimize the loss or addition of information (refer to b)
of S 4.1 above).

   If a signal possesses information elements which are not present in the
signals of the other signalling system with which interworking should take
place, the information concerned cannot be transmitted and the appropriate
performance feature cannot be utilized (refer to c) of S 4.1 above).

   In a few cases special procedures have to be laid down if the status of the
connection does not permit transmission of the intended interworking signal.
If conversion is not possible with certain backward signals, it may be
necessary to apply a corresponding tone (see Recommendation Q.35).

   In addition, there are cases in which the information content of several
signals of one of the signalling systems has to be converted so as to obtain
one signal of the other signalling system and vice versa.


                             ____________________
                             Recommendation Q.605
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
5 :  DRAWING CONVENTIONS
~~~~~~~~~~~~~~~~~~~~~~~~
   In addition to Recommendations Z.101 to Z.104, the following rules apply to
the logic procedures of the interworking specifications.



 * 5.1 :  Inputs and outputs

   In accordance with the basic concepts of SDL, internal | inputs and outputs
are used for logic procedures that do not go beyond the functional block
involved.  In addition, some SPITEs are used as internal inputs to describe
the information flow at the interface between the signalling and switching
procedures.

   All other inputs and outputs, including FITEs and BITEs as well as signals,
which pass from one functional block to another are considered as being
external .

   The external | inputs and outputs point in the direction of the data flow
between the three functional blocks as shown in Figure 2/Q.602.

   A multiple input (i.e.  a group of signals) which leads to one and the same
procedure can be represented by one standard symbol including that group of
signals, if possible.



 * 5.2 :  States

   State symbols shall contain

   o The state number; and

   o The descriptive text of the state.

   Most frequently the state indicates the input being waited for.

   The layout of the state symbol to be used for the interworking
specifications is given in Figure 3/Q.605.

                                                        Figure 3/Q.605, p.

 * 5.3 :  Connectors

   Connectors are represented by a circle.  The in-connector labels (within
the connector symbol) shall be unique within the same interworking diagram.

   The designations used within the connector symbols are as follows (see
Figure 4/Q.605):

   a) Arabic numerals, where the vertical line of flow of the procedure is to
      be interrupted.  Subscripts outside the connector indicate the sheet
      numbers on which the associated connec- tors appear;

   b) Capital letters, where the horizontal line of a multiple branching of
      the process is to be interrupted.  Subscripts outside the connectors
      indicate the sheet numbers, on which the associated connectors appear;

   c) "Pi" to indicate that the procedures are not completed (e.g.  a
      subroutine or another detailed procedure).  The connector symbol will
      then be non-subscripted with sheet numbers but be provided with the
      comment "to be completed" associated with a reference to the
      Recommendation concerned, if any.

   The connector reference is always shown in the left-hand column of each
sheet of the interworking diagrams.

                                                         Figure 4/Q.605 p.

 * 5.4 :  Procedures not presented

   In general, possible signals which are not shown as inputs in a given state
are to be considered as consumed but discarded, i.e.  ignored.  A special
treatment may be required in the following cases:

   a) electrical conditions not recognized as regular signals (e.g.  1 out of
      6 frequencies in the case of MFC signalling);

   b) regular signals, but not relevant to interworking (e.g.  blocking,
      identification);

   c) any other regular signal recognized as an abnormality (e.g.  out of
      sequence).

   In the cases a) and c), the appropriate actions to be taken are not
specified in the existing Recommendations.  Further study is required.

   The reactions in case of signals out of sequence can be shown by means of a
state/signal matrix as auxiliary documentation.  The interpretation of the
diagrams will then be unambiguous.



 * 5.5 :  Presentation of time supervision

   The method of time supervision presentation to be used is shown in Figure
5/Q.605.

   If two timers are running in a state such that the longer timer can never
mature, the input "time release" should nevertheless be shown for both timers
in order that no misunderstanding can result.  The meaning of start t1also
includes the possibility of restart t1, t1 means the expiry of t1.

                                                       Figure 5/Q.605, p.5

 * 5.6 :  Storage of inputs

   During the method of register function activation, all inputs are
implicitly stored and the sequence of FITEs is also recorded.  When the
register function is not activated, inputs must explicitly be stored if
required in a later state transition.



 * 5.7 :  Method of changing the order of signals

   In several interworking situations, the order in which signals are received
is not necessarily the order of their utilization.  Therefore, a rearrangement
of the order is necessary.  To change the signalling sequence in the
interworking diagrams, the method indicated in Figure 6/Q.605 should be
applied.  Figure 6/Q.605 shows how such a situation can be coped with by SDL.



 * 5.8 :  Multiple sending of FITEs 1 or digits

   The case of multiple sending of FITEs 1 or digits often occurs in the logic
procedures:  in the former case in the incoming or interworking procedures,
and in the latter case in the outgoing procedures of the en-bloc Signalling
Systems No.  5 and R1.  The presentation of Figure 7/Q.605 should be used.  a)
of Figure 7/Q.605 is used for multiple FITEs 1, while b) of Figure 7/Q.605 is
used for outgoing Signalling Systems No.  5 or R1.  In b) of Figure 7/Q.605
the outgoing logic has already received all the FITEs 1 and has established
the "ST condition" prior to the logic sequence shown.

                                                       Figure 6/Q.605, p.6

                                                       Figure 7/Q.605, p.7



 * 5.9 :  Different signalling speeds

   In interworking cases where the signalling system at the outgoing end uses
the overlap signalling mode with acknowledgements (Signalling Systems No.  4
and R2) or where the signalling speed of the system at the outgoing end is
lower than that at the incoming end, the presentation method indicated in
Figure 8/Q.605 should be used.

                                                        Figure 8/Q.605, p.


                             ____________________
                             Recommendation Q.606
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
6 :  LOGIC PROCEDURES
~~~~~~~~~~~~~~~~~~~~~
   The logic procedures are prepared as:

   a) Logic procedures for incoming signalling systems,

   b) Interworking logic procedures,

   c) Logic procedures for outgoing signalling systems.

   A state overview diagram is provided with each procedure.  The state
overview diagram:

   o Lists the states for the logic,

   o Provides a sheet reference for each state, and

   o Shows permitted transitions between states.

   In addition, notes and timers are provided.



 * 6.1 :  Incoming signalling system logic procedures

   In specifying the logic procedures the following elements are used:

   a) Inputs in the form of forward signals,

   b) Outputs in the form of FITEs,

   c) Inputs in the form of BITEs,

   d) Outputs in the form of backward signals,

   e) Time supervision arrangements,

   f) Routing and switching aspects that are needed for interworking (SPITEs).

   Incoming signalling system logic procedures are provided for:

   o Signalling System No.  4 in Recommendation Q.611,

   o Signalling System No.  5 in Recommendation Q.612,

   o Signalling System No.  6 in Recommendation Q.613,

   o Signalling System No.  7 (TUP) in Recommendation Q.614,

   o Signalling System R1 in Recommendation Q.615,

   o Signalling System R2 in Recommendation Q.616.



 * 6.2 :  Interworking logic procedures

   In specifying the logic procedures the following elements are used:

   a) Inputs in the form of FITEs from the incoming signalling system,

   b) Outputs in the form of FITEs to the outgoing signalling system,

   c) Inputs in the form of BITEs from the outgoing signalling system,

   d) Outputs in the form of BITEs to the incoming signalling system,

   e) Routing and switching aspects that are needed for interworking (SPITEs).

   Interworking logic procedures can be provided for every possible
combination of CCITT Signalling Systems.

   The following interworking combinations are provided:

   o Signalling System No.  4 to R2 in Recommendation Q.634,

   o Signalling System No.  5 to No.  6 in Recommendation Q.642,

   o Signalling System No.  5 to No.  7 (TUP) in Recommendation Q.643,

   o Signalling System No.  5 to R1 in Recommendation Q.644,

   o Signalling System No.  5 to R2 in Recommendation Q.645,

   o Signalling System No.  6 to No.  5 in Recommendation Q.652,

   o Signalling System No.  6 to No.  7 (TUP) in Recommendation Q.653,

   o Signalling System No.  6 to R1 in Recommendation Q.654,

   o Signalling System No.  6 to R2 in Recommendation Q.655,

   o Signalling System No.  7 (TUP) to No.  5 in Recommendation Q.662,

   o Signalling System No.  7 (TUP) to No.  6 in Recommendation Q.663,

   o Signalling System No.  7 (TUP) to No.  7 in Recommendation Q.664,

   o Signalling System No.  7 (TUP) to R1 in Recommendation Q.665,

   o Signalling System No.  7 (TUP) to R2 in Recommendation Q.666,

   o Signalling System R1 to No.  5 in Recommendation Q.671,

   o Signalling System R1 to No.  6 in Recommendation Q.672,

   o Signalling System R1 to No.  7 (TUP) in Recommendation Q.673,

   o Signalling System R1 to R2 in Recommendation Q.674,

   o Signalling System R2 to No.  4 in Recommendation Q.681,

   o Signalling System R2 to No.  5 in Recommendation Q.682,

   o Signalling System R2 to No.  6 in Recommendation Q.683,

   o Signalling System R2 to No.  7 (TUP) in Recommendation Q.684,

   o Signalling System R2 to R1 in Recommendation Q.685.



 * 6.3 :  Outgoing signalling system logic procedures

   In specifying the logic procedures, the following elements are used:

   a) Inputs in the form of FITEs,

   b) Outputs in the form of forward signals,

   c) Inputs in the form of backward signals,

   d) Outputs in the form of BITEs,

   e) Time supervision arrangements,

   f) Routing and switching aspects that are needed for interworking (SPITEs).

   Outgoing logic procedures are provided for:

   o Signalling System No.  4 in Recommendation Q.621,

   o Signalling System No.  5 in Recommendation Q.622,

   o Signalling System No.  6 in Recommendation Q.623,

   o Signalling System No.  7 (TUP) in Recommendation Q.624,

   o Signalling System R1 in Recommendation Q.625,

   o Signalling System R2 in Recommendation Q.626.


                             ____________________
                             Recommendation Q.607
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
7 :  INTERWORKING REQUIREMENTS FOR NEW SIGNALLING SYSTEMS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * 7.1 :  Treatment of new signals in another signalling system

   In order to facilitate the interworking between new signalling systems and
existing ones, it is desirable to elaborate rules to be taken into account
when specifying the new signalling system(s).  Since compatibility between all
CCITT Signalling Systems must be ensured, any newly developed system has to
meet the following requirements with regard to interworking:

   a) New signalling systems should be capable of processing all interworking
      events specified for the existing signalling systems without losing or
      adding information elements.

      This is best achieved by the concept of transparency, whereby the
      signals of all existing systems have a unique translation into the new
      system and back again.  In this way a tandem connection via an
      interposed link employing the new signalling system will neither add nor
      subtract from the information transfer that would otherwise have
      occurred had the new signalling system not been present;

   b) Newly developed systems should not lead to any modification to the
      specifications covering the present signalling systems except that the
      translation of new interworking events arising from the meanings of new
      signals in the new system will need to be defined for the existing
      signalling systems.

      In order that the new signals should cause the minimum loss or gain of
      information when interworking with existing signalling systems, any new
      signals should, if possible, not contain any information elements
      already existing.  Hence it is better that these new signals convey only
      a single meaning rather than a multiple meaning as occurs in some
      existing systems (e.g.  Signalling System R2 signal I-14 corresponds to
      FITE 8 which combines the elements of FITE 3 and FITE 5).  Therefore,
      only one new information element will be associated with the new signal
      and only one new FITE or BITE will be needed.

      In some cases the new signal will be translated into a presently defined
      signal of an existing system and hence will cause the addition or, more
      often, the loss of information.  In some cases, no electrical signal
      being available, all the information may be lost or a tone may need to
      be used.  In the case of Signalling Systems R2, No.  6 and No.  7, some
      reserved signals exist within the capacity of these systems and such
      signals may be introduced to enhance the signalling system and provide
      an interworking capability.

      However it should be borne in mind that with such existing systems, it
      may not be easy or desirable to modify existing equipment, and even if
      such modification were possible, in the transitional period the
      interworking of existing and enhanced signalling equipment of the same
      system must also be considered.

      In view of the difficulties of interworking with existing signalling
      systems, new features of signals should only be introduced in a new
      system if there are good operational reasons for doing so.



 * 7.2 :  Reserve for national use

   In practice, provision of appropriate spare signalling capacity in a new
system reserved for national/regional use cannot be avoided.  In such a case,
precautions must be taken to prevent signals with an individual national
meaning from entering the international network.

   One general objective of a new signalling system should be to meet also the
national requirements in order to avoid national ver- sions of a given
signalling system as far as possible.



 * 7.3 :  Unambiguous specifications

   After a clear specification of a new feature to be included in a signalling
system, the related signalling procedures should be specified in a unique and
standard form.  The same applies to the signals involved.

   The designation of signals of different signalling systems, which carry the
same information, should be the same.



 * 7.4 :  Escape codes

   It is obvious that appropriate spare capacity should be provided in order
to cope with future demands.  One way of doing so is the provision of escape
codes.



                             ____________________
                             Recommendation Q.608
                             ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
8 :  MISCELLANEOUS INTERWORKING ASPECTS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   In producing the interworking specifications in the present form some
interworking aspects were found, which are not covered by the specifications
of the signalling systems themselves and need to be taken into account when
using the SDL diagrams for interworking specification.



 * 8.1 :  Transfer of no charge information

   Difficulties related to the use of charge or no charge information were
recognized by CCITT for the following reasons:

   In the case of interworking with systems not able to provide the no charge
information together with the answer signal, a no charge call is only possible
by withholding the answer signal.  In the international network, the absence
of the answer signal results in a time-out within a delay period of 2 to 4
minutes as described in Recommendation Q.118, which considers this situation
to be abnormal.  Thus for certain cases of interworking, intentional
withholding of the answer signal would be identical with the abnormal
condition.  Thus discrimination is impossible.

   It is recommended that:

   a) Withholding the answer signal cannot be a satisfactory solution since:

      o The connection may remain in the abnormal transmission condition (e.g.
        failure to enable the echo suppressor in Signalling System R2 and
        retention of band-stop filter in Signalling System R1),

      o The time supervision will interrupt the connection after 2 or 4
        minutes, and the answer signal should thus be retained (be used) even
        in the case of a no charge condition over the international network;


   b) There is no necessity to modify existing equipment to provide charge/no
      charge information transfer capabilities.

   From a technical viewpoint, international no charge | alls are possible
without restrictions only when the Signalling Systems No.  6, No.  7 (TUP) or
R2 are used exclusively throughout the entire international network (assuming
that no charge information is received from the national network).

   In the case of interworking with systems not able to transfer the no charge
| nformation, a no charge call can at present only be provided by withholding
the answer signal.  Consequently the transfer of no charge information must
not be performed in these cases.

   In the case of Signalling System No.  6, the information no charge | would
be sent together with the address-complete, no charge information is
contradicted by the subsequent answer, charge signal the call should
nevertheless not be charged (S 4.1.9, Signalling System No.  6 specification).

   When interworking from Signalling System No.  6 or No.  7 (TUP) to
Signalling System R2 the comments of S 8.1 have to be taken into account.  The
transfer of no charge Information is possible when interworking from any of
the Signalling Systems:  No.  6 , No.  7 (TUP) and R2 to any of the Signalling
Systems:  No.  6, No.  7 (TUP) and R2.


 * 8.2 :  Time-out guidelines

8.2.1 Time-outs connected with subscribers' behaviour
~~~~~
      The specified register time-out of 4 to 6 seconds (after each digit is
      received which is resorted to when address complete cannot be identified
      in another way) has proved to give satisfactory technical functioning at
      least in those cases where the exception described in Recommendation
      Q.261, S 4.1.5, e) does not apply.

      Insufficient information is obtained to motivate a change at this stage
      of the duration of the 4 to 6 seconds time-out specified in the outgoing
      register in cases where no address-complete indication is available.

      It is recommended that the 4 to 6 seconds interdigital time-out
      procedure should be used where needed only.  It is furthermore
      recommended that Administrations make their network numbering known to
      their respondents so that maximum use of number length analysis can be
      made whenever address-complete information cannot be given.


8.2.2 General time-out guidelines for new signalling systems
~~~~~
      i) 20-30 seconds is considered to be the proper time-out interval for
         outgoing registers for non-receipt of address signals, or address
         complete.

     ii) When backward signals are provided, if the address-complete signal is
         not available before 15-20 seconds after the last received address
         signal at the incoming register, then an address incomplete signal
         should be sent.  If, however, it is known that the address is
         complete, then the time-out should be extended to 20-30 seconds.

    iii) If it is known that a positive (real) address-complete signal is
         available but will not be returned within the lower limit of the
         20-30 second time-out period of the outgoing register then an
         artificial address-complete signal should be sent within 15-20
         seconds.  The indiscriminate use of such a sig- nal should be
         avoided.  A new "call-in-progress" signal should not be used instead
         of the "artificial address-complete" signal.

     iv) When backward signals are not available and complete number length
         analysis in the outgoing register is not practical, then the 4-6
         seconds time-out is used to determine address complete instead of the
         20-30 seconds time-out mentioned in point i).  This time-out
         commences when the minimum number length has been reached.  The
         number length is determined when the time-out matures or if the known
         maximum number length is received.


8.2.3 General time-out guidelines for existing signalling systems
~~~~~
      These guidelines are primarily intended for signalling on international
      calls where fully overlap digit sending can occur.  Other guidelines may
      be appropriate to some national applications.

      During call set up both incoming and outgoing registers are normally
      supervised by timers.  The duration of the time-out interval is defined
      in the relevant Recommendations defining the signalling systems.  These
      are summarised in the table below.  In the case of a multi-link
      connection with overlap signalling, the time between digit transmission
      or reception will be supervised at each exchange, and according to
      existing Recommendations, at both incoming and outgoing registers in
      each exchange.  It is considered that this situation is unsuitable since
      the cleardown of a call where insufficient digits are dialled can lead
      to unpredictable results because of the possibility of timers expiring
      in a different order on subsequent call attempts.  In some cases this
      can lead to different tones being returned to the calling subscriber on
      subsequent calls.  Since the first to expire and therefore normally the
      controlling time-out will be the incoming register time-out of around
      15-20 seconds, it is recommended that this time-out should only be
      activated at a single point in the connection at any stage of call set
      up.  The most suitable point is the incoming register at the exchange
      closest to the called subscriber at any point in the call set up.  To
      achieve this it is recommended that the incoming register time-out
      should be inhibited at each exchange once the outgoing circuit has been
      seized.  The longer time-out of around 20-30 seconds which will be
      active at outgoing registers, and in some cases incoming registers also,
      should not be inhibited.

      This feature need not be implemented at existing exchanges or for
      Signalling System No.  4 which has time-outs not in conformance with
      modern practice.


8.2.4 Summary of inter-digital time-outs
~~~~~

                                 H.T. [T1.608]

 ______________________________________________________________________________________________________________________________________
                                                                         Signalling System
     Type of time-out           4               5                   6                      7                   R1               R2
 ______________________________________________________________________________________________________________________________________
  Outgoing                   15-30 s                             20-30 s                20-30 s                               > | 4 s
                              Q.127                               Q.268                  Q.724                                 Q.476
                           S 4.4.1.2a.2                       S 4.8.5.1(a)              S 6.4.1                              S 5.5.1.2
 ______________________________________________________________________________________________________________________________________
  Incoming                   30-60 s         10-20 s             15-20 s                15-20 s              10-20 s           8-24 s
  Receipt of digit                               {
  (to KP signal)
  20-40 s
  typical (to ST signal)
   }                                                         (to ST signal)      (15-24 s)  (preferr
                              Q.127          Annex 2              Q.261                  Q.724                Q.325            Q.476
                           S 4.4.3(2)a    Tables 4 and 6         S 4.1.6                 S 1.7              S 3.6.2.2        S 5.5.2.1
 ______________________________________________________________________________________________________________________________________
  Outgoing                                    4-6 s                                                           4-6 s
   {
  Determination of
  ST condition
   }                                      Q.152  S 3.2.1                                               Q.321  S 3.2.1b(ii)
 ______________________________________________________________________________________________________________________________________
  Incoming                                                       20-30 s                20-30 s
   {
  Time-out after
  ST received
   }                                                       Q.268  S 4.8.5.3(a)     Q.724  S 6.4.3(a)_____________________________________________________________________________________________________________________________________


                                                        TABLE [T1.608], p.


 * 8.3 :  Reset procedures

8.3.1 When the reset signal is received on an incoming Signalling System No.
~~~~~ 6 or 7 (TUP) circuit the succeeding circuit is released by the
clear-forward procedure in all cases.


8.3.2 When the reset signal is received on an outgoing Signalling System No.
~~~~~ 6 or 7 (TUP) circuit the response is:

      i) To initiate the clear-forward sequence on the outgoing circuit;

     ii) To release exchange equipment as appropriate, ie:  SPITE 3 in the
         register phase and SPITE 5 in the speech phase;

    iii) To return an appropriate signal and/or tone on the incoming circuit
         as shown in the following table.


                                 H.T. [T2.608]

       _______________________________________________________________________________________________
        Signalling  System No.           Register phase          Wait for answer   Answered   Clear-k
       _______________________________________________________________________________________________
                   |                       Busy flash              Busy flash
        Clear-back + congestion
           tone if possible
                   }              Congestion tone  if possible
                   |                       Busy flash              Busy flash
                   |                          CFL                      CFL
                7 (TUP)                       CFL                      CFL
                  R1                    Congestion tone          Congestion tone
                  R2                         A4/B4               Congestion tone



                                                                                    {




       _______________________________________________________________________________________________

                                                    Tableau [T2.608], p.10



                                     ANNEX A
                        (to Recommendations Q.601-Q.608)

                 Lists and meanings of FITEs, BITEs and SPITEs.

               Representation of information contents of signals
                           of the Signalling Systems.
                                 H.T. [1T3.608]
                                    TABLE A-1
             List of forward interworking telephone events (FITEs)





















       _________________________________________________________________________________________________________________________________









                                    No.                                        {


                                                                                           No. 4   N5   No. 6   No. 7  (TUP)   R1    R2
 _________________________________________________________________________________________________________________________________
                                1                                 {
   Digit 1, 2, . |  |  9 or 0, code 11 or 12, end-of-pulsing
                          (ST) signal
                                }                                 1                    1       1    1           1         1
 _________________________________________________________________________________________________________________________________
                                2                                 {
       Country-code indicator, country code not included
                                }                                 8                    8       2    2                    18
 _________________________________________________________________________________________________________________________________
                                3                                 {
         Country-code indicator, country code included
                                }                                 9                    9       3    3
 _________________________________________________________________________________________________________________________________
                                4                                 {
    Echo-suppressor indicator, outgoing half-echo suppressor
    not included, incoming half-echo suppressor not required
                                }                                                              6    6                    19
 _________________________________________________________________________________________________________________________________
                                5                                 {
    Echo-suppressor indicator, outgoing half-echo suppressor
        included, incoming half-echo suppressor required
                                }                                10                            7    7                    11
 _________________________________________________________________________________________________________________________________
                                6                                 {
         Country-code indicator, country code included;
  echo-suppressor indicator, outgoing half-echo suppressor not
        included, outgoing half echo suppressor required
                                }                                                                                         8
 _________________________________________________________________________________________________________________________________
                                7                                 {
         Country-code indicator, country code included;
  echo-suppressor indicator, outgoing half-echo suppressor not
             included, no echo suppressor required
                                }                                                                                         9
 _________________________________________________________________________________________________________________________________
                                8                                 {
         Country-code indicator, country code included;
    echo-suppressor indicator, outgoing half-echo suppressor
        included, incoming half-echo suppressor required
                                }                                                                                        10
 _________________________________________________________________________________________________________________________________
                                9                                 {
     Calling-party's-category indicator, operator, language
                             French
                                }                                 2                    2       8    8                     2
 _________________________________________________________________________________________________________________________________
                               10                                 {
     Calling-party's-category indicator, operator, language

                              English
                                }                                 3                    3       9    9                     3
 _________________________________________________________________________________________________________________________________
                               11                                 {
     Calling-party's-category indicator, operator, language
                             German
                                }                                 4                    4      10    0                     4
 _________________________________________________________________________________________________________________________________
                               12                                 {
     Calling-party's-category indicator, operator, language
                            Russian
                                }                                 5                    5      11    1                     5
 _________________________________________________________________________________________________________________________________
                               13                                 {
     Calling-party's-category indicator, operator, language
                            Spanish
                                }                                 6                    6      12    2                     6
 _________________________________________________________________________________________________________________________________
                               14                                 {
       Calling-party's-category indicator, operator with
                   forward-transfer facility
                                }                                                                                        15
 _________________________________________________________________________________________________________________________________
                               15                                 {
         Calling-party's-category indicator, subscriber
                                }                                                                                         7
 _________________________________________________________________________________________________________________________________
                               16                                 {
       Calling-party's-category indicator, subscriber or
           operator without forward-transfer facility
                                }                                                                                        12
 _________________________________________________________________________________________________________________________________


                                                    Tableau [1T3.608] p.11



                                 H.T. [2T3.608]
                               TABLE A-1 (cont.)



       _________________________________________________________________________________________________________________________________________










                                        No.                                            {


                                                                                                     4   No. 5   No. 6   No. 7  (TUP)   R1   R2
       _________________________________________________________________________________________________________________________________________
                                        17                                     {
           Calling-party's-category indicator, subscriber, ordinary call
                                         }                                     7                          13      13
       _________________________________________________________________________________________________________________________________________
                                        18                                     {
        Calling-party's-category indicator, subscriber, call with priority
                                         }                                                                14      14                    14
       _________________________________________________________________________________________________________________________________________
                                        19                                     {
                   Calling-party's-category indicator, data call
                                         }                                                                15      15                    13
       _________________________________________________________________________________________________________________________________________
                                        20                                     {
        Nature-of-circuit indicator, no satellite circuit in the connection
                                         }                                                                 4       4                    20
       _________________________________________________________________________________________________________________________________________
                                        21                                     {
             Nature-of-circuit indicator, one satellite circuit in the
                                    connection
                                         }                                                                 5       5                    21
       _________________________________________________________________________________________________________________________________________
                                        22                                    Clear-forward               10      16          16         3   16
       _________________________________________________________________________________________________________________________________________
                                        23                                    Forward-transfer            11      17          17         2
       _________________________________________________________________________________________________________________________________________
                                        24                                    Continuity                          18          18
       _________________________________________________________________________________________________________________________________________
                                        25                                     {
                   Continuity-check indicator, continuity check
                                   not required
                                         }                                                                        21
       _________________________________________________________________________________________________________________________________________
                                        26                                     {
                   Continuity-check indicator, continuity check
                             required on this circuit
                                         }                                                                        20
       _________________________________________________________________________________________________________________________________________
                                        27                                     {
              Continuity-check indicator, continuity check being done
                                on previous circuit
                                         }                                                                        22
       _________________________________________________________________________________________________________________________________________
                                        28                                    Spare
       _________________________________________________________________________________________________________________________________________
                                        29                                    Spare
       _________________________________________________________________________________________________________________________________________
                                        30                                    Service information                             23









       _________________________________________________________________________________________________________________________________________
                                        31                                     {
                           General set-up message (GSM)
                                         }                                                                        24
       _________________________________________________________________________________________________________________________________________

                                                    Tableau [2T3.608] p.12





 * A.1 :  Explanatory notes on the meanings and uses of FITEs | see Table A-1)

   These are Forward Interworking Telephone Events sent from an incoming
procedure to an interworking procedure, or from an interworking procedure to
an outgoing procedure.

A.1.1 FITE 1 means one of the digits 1-9, 0, code 11, code 12 and code 15
~~~~~ (ST), when used as an address signal (i.e.  not including their use for
other information, e.g.  language digits).  Each FITE 1 represents one digit
only and that digits value is implicit in the signal.


A.1.2 FITEs 2, 3, 6, 7 and 8 are events representing country code indicators.
~~~~~ These signals are not sent from the incoming procedure to the
interworking procedure, since the country code indicator is a link dependent
signal and is used by the incoming procedure as part of the input information
to the digit analysis.  These FITEs are generated in the interworking
procedure by the use of SPITE 22 (see Table A-3).


A.1.3 FITEs 4-8 are events representing echo-suppressor indicators.  These
~~~~~ signals are not sent from the incoming procedure to the interworking
procedure, since the echo-suppressor indicator is a link dependent signal and
is used by the incoming procedure as part of the input information to the
digit analysis.  These FITEs are generated in the interworking procedure by
the use of SPITE 21 (see Table A-3).


A.1.4 FITEs 9-19 are events representing calling-party's category indicators
~~~~~ | nd include telephone events derived from language digits,
discriminating digits and calling-party's-category signals.


A.1.5 FITEs 20 and 21 are events representing nature-of-circuit indicators.
~~~~~ These signals are not sent from the incoming procedure to the
interworking procedure, but the nature-of-circuit indicator is used by the
incoming procedure as part of the input information to the digit analysis.
These FITEs are generated in the interworking procedure by the use of SPITE 20
(see Table A-3).  These signals are not completely link dependent, since if
the nature-of-circuit indicator on the incoming circuit implies one satellite
in the connection, the same signal (FITE 21) will be sent to the outgoing
procedure.


A.1.6 FITE 22 is an event representing the clear-forward signal and overrides
~~~~~ all other procedures.  It should therefore be shown as an input in all
call states except idle, even though the waiting state might not appear to be
capable of receiving FITE 22.


A.1.7 FITE 23 is an event representing the forward-transfer signal | nd is
~~~~~ assumed to be capable of reception after the state Address-complete when
the register function is deactivated and the speech condition is set up.


A.1.8 FITE 24 is an event representing the continuity signal | n common
~~~~~ channel signalling systems.  When interworking from a channel associated
signalling system to a common channel signalling system, FITE 24 must be
generated by the interworking procedure.


A.1.9 FITEs 25, 26, 27 are events which define the continuity check
~~~~~ requirements on outgoing circuits for common channel systems.


A.1.10 FITE 30 is an event which defines the Services which have been
~~~~~~ requested and can be provided e.g., Speech, Closed User Group, Digital
Connectivity, etc.


A.1.11 FITE 31 is an event which defines the information to be carried by the
~~~~~~ General Set-up Message (GSM).



 * A.2 :  Explanatory notes on the meanings and uses of BITEs | see Table A-2)

   These are Backward Interworking Telephone Events sent from an outgoing
procedure to an interworking procedure, or from an interworking procedure to
an incoming procedure.

A.2.1 BITE 2 is an address-complete event | hich may be originated either by
~~~~~ the receipt of an address complete signal or by the simulation of the
address complete condition from a signalling system not employing address
complete signals.  This latter event is designated BITE 26, when signalling
from the outgoing procedure to the interworking procedure.  Since in most
cases the forward signalling continues beyond the time that the
address-complete is simulated, BITE 2 does not cause register deactivation in
the incoming logic in the way that BITEs 3-7 do.  The incoming procedure must
wait for the subsequent reception of BITE 27 or BITE 28 (see SS A.2.7 and
A.2.8).


A.2.2 BITEs 3-7 are address-complete events | hich cause the speech condition
~~~~~ to be set up and the register function to be deactivated.


A.2.3 BITEs 8-17, 19, 20 are call unsuccessful events | hich cause the return
~~~~~ of a corresponding event to the incoming procedure where the register
function will be deactivated.  They are separated according to the reasons of
an unsuccessful call.


A.2.4 BITEs 21-24 are answer events , differentiated where possible.
~~~~~

A.2.5 BITE 25 is the event representing the clear-back signal.
~~~~~

A.2.6 BITE 26 is an event signalling the simulation of address-complete
~~~~~ condition by an outgoing signalling system which does not employ
address-complete signals (e.g.  No.  5 or R1).  If the incoming signalling
system uses address-complete signals, BITE 26 is translated to BITE 2 in the
interworking procedures, in other cases it is discarded.

A.2.7 BITE 27 means that an outgoing signalling system which does not employ
~~~~~ address-complete signals has completed forward signalling | e.g.  ST has
been sent) and the speech condition should be set up used, it will follow
after BITE 26.

      For incoming signalling systems employing address-complete signals, BITE
27 will always be expected after BITE 2.  Therefore when both interworking
systems employ address-complete signals, the interworking procedure must
translate BITE 2 to BITE 2 + BITE 27.


A.2.8 BITE 28 is used only from an interworking procedure to an incoming
~~~~~ procedure in the case where a BITE is received from the outgoing
procedure which has no corresponding BITE in the incoming procedure.  A tone
will be returned by the use of SPITE 6 in the interworking procedure, and BITE
28 is used solely to deactivate the register function in the incoming
procedure.


A.2.9 BITE 29 release incoming side , is used from an interworking procedure
~~~~~ to an incoming procedure for incoming systems where release procedures
may be initiated in the backward direction (e.g.  the INMARSAT signalling
system).


A.2.10 BITE 30 switchthrough may be completed | s used to signal from an
~~~~~~ outgoing procedure to an incoming procedure via the relevant
interworking, that the speech path may be connected through.


A.2.11 BITE 31 is an event which requests the information asked for by the
~~~~~~ General Request Message (GRQ).


A.2.12 BITE 35 is a call unsuccessful event corresponding to the receipt of
~~~~~~ the Access Barred Signal (ACB).  This BITE is used e.g.  in Closed User
Group calls.


A.2.13 BITE 36 is a call unsuccessful event that occurs when a digital path
~~~~~~ cannot be provided.

       Note - Bites 35 and 36 are only used in No.  7 originated calls.




                                 H.T. [1T4.608]
                                    TABLE A-2
             List of backward interworking telephone events (BITEs)

       _____________________________________________________________________________________________________________________________________________________







                                       No.                                                {

                                                                                                       No. 4   No. 5   No. 6   No. 7  (TUP)      R1      R2
       _____________________________________________________________________________________________________________________________________________________
                                         1                                   Spare
       _____________________________________________________________________________________________________________________________________________________
                                         2                                   Address-complete, charg     1               1           1                    2
       _____________________________________________________________________________________________________________________________________________________
                                         3                                    {
                           Address-complete, no charge
                                         }                                                                      2        2
       _____________________________________________________________________________________________________________________________________________________
                                         4                                   Address-complete, coin                      3           3
       _____________________________________________________________________________________________________________________________________________________
                                         5                                    {
                    Address-complete, subscriber free, charge
                                         }                                                                      4        4                    8 and 13
       _____________________________________________________________________________________________________________________________________________________
                                         6                                    {
                   Address-complete, subscriber free, no charge
                                         }                                                                      5        5                     9
       _____________________________________________________________________________________________________________________________________________________
                                         7                                    {
                   Address-complete, subscriber free, coin box
                                         }                                                                      6        6
       _____________________________________________________________________________________________________________________________________________________
                                         8                                   Call unsuccessful           2       1
       _____________________________________________________________________________________________________________________________________________________
                                         9                                    {
                Call unsuccessful, switching-equipment congestion
                                         }                                                                       7       7
       _____________________________________________________________________________________________________________________________________________________
                                        10                                    {
                   Call unsuccessful, circuit-group congestion
                                         }                                                                       8       8
       _____________________________________________________________________________________________________________________________________________________
                                        11                                    {
        Call unsuccessful, switching-equipment congestion or circuit group
                                    congestion
                                         }                                                                                                     3
       _____________________________________________________________________________________________________________________________________________________
                                        12                                    {
                  Call unsuccessful, national-network congestion
                                         }                                                                       9       9                     1
       _____________________________________________________________________________________________________________________________________________________
                                        13                                    {
                  Call unsuccessful, address-complete, national
                                network congestion
                                         }                                                                                                    6 and 15
       _____________________________________________________________________________________________________________________________________________________
                                        14                                    {
                      Call unsuccessful, address incomplete
                                         }                                                                      10      10









       _____________________________________________________________________________________________________________________________________________________
                                        15                                    {
            Call unsuccessful, (address-complete), unallocated number
                                         }                                                                      11      11                    7 and 14
       _____________________________________________________________________________________________________________________________________________________
                                        16                                    {
           Call unsuccessful, address-complete, subscriber busy (elec.)
                                         }                                                                      12      12                     5
       _____________________________________________________________________________________________________________________________________________________
                                        17                                    {
             Call unsuccessful, address-complete, line out of service
                                         }                                                                      13      13                    10
       _____________________________________________________________________________________________________________________________________________________
                                        18                                   Spare
       _____________________________________________________________________________________________________________________________________________________
                                        19                                    {
                         Call unsuccessful, call-failure
                                         }                                                                      15      15
       _____________________________________________________________________________________________________________________________________________________
                                        20                                    {
                 Call unsuccessful, send special information tone
                                         }                                                                      14      14                    4 and 14
       _____________________________________________________________________________________________________________________________________________________
                                        21                                   Answer, subscriber free                                                     11
       _____________________________________________________________________________________________________________________________________________________
                                        22                                    {
                         Answer, subscriber free, charge
                                         }                                   3                           2      16      16          1
       _____________________________________________________________________________________________________________________________________________________
                                        23                                    {
                        Answer, subscriber free, no charge
                                         }                                                                      17      17
       _____________________________________________________________________________________________________________________________________________________
                                        24                                   Answer, re-answer                          18          18
       _____________________________________________________________________________________________________________________________________________________
                                        25                                   Clear-back                  4       3      19          19           2       12
       _____________________________________________________________________________________________________________________________________________________



                                                    Tableau [1T4.608] p.13



                                 H.T. [2T4.608]
                               TABLE A-2 (cont.)






















       ___________________________________________________________________________________________________________________________________







                                No.                                         {

                                                                                              No. 4 o. 5   No. 6   No. 7  (TUP)   R1   R2
       ___________________________________________________________________________________________________________________________________
                                26                             {
             Artificial address complete is sent | ua)
                                 }                                                            4                    3
       ___________________________________________________________________________________________________________________________________
                                27                             {
          Sending-finished; set up speech condition | ua)
                                 }                                                            5                    4
       ___________________________________________________________________________________________________________________________________
                                28                             {
                Deactivate register function | ua)
                                 }
       ___________________________________________________________________________________________________________________________________
                                29                             {
                    Release incoming side | ua)
                                 }
       ___________________________________________________________________________________________________________________________________
                                30                             {
               Switchthrough may be completed | ua)
                                 }
       ___________________________________________________________________________________________________________________________________
                                31                            General request message (GRQ)                             20
       ___________________________________________________________________________________________________________________________________
                                32                            Spare
       ___________________________________________________________________________________________________________________________________
                                33                            Spare
       ___________________________________________________________________________________________________________________________________
                                34                            Spare
       ___________________________________________________________________________________________________________________________________
                                35                             {
                 Call unsuccessful, access barred
                                 }                                                                         21
       ___________________________________________________________________________________________________________________________________
                                36                             {
        Call unsuccessful, digital patch not provided (DPN)
                                 }
                                22
       ___________________________________________________________________________________________________________________________________

       a) These signals do not necessarily correspond to a backward signal
       but correspond to logic events.
                                                    Tableau [2T4.608] p.14




                                 H.T. [1T5.608]
                                    TABLE A-3

               List of switching processing interface telephone
                                events (SPITEs)


       ____________________________________________________________________________________________________________________
                                         No.                                            Designation             Symbol
       ____________________________________________________________________________________________________________________
                                          1                                      {
        Activate register function (physical register or equivalent function)
                                          }                                     Task
                                          2                                     Register function acated    Internal input
                                          3                                     Deactivate register ction        Task
                                          4                                     Set up speech condit             Task
                                         4A                                     Speech path may be sup           Task
                                          5                                      {
                 Release speech condition (of the speech path in the
                                      exchange)
                                          }                                     Task
                                          6                                     Return appropriate t             Task
                                          7                                     Disconnect tone                  Task
                                          8                                      {
             Release all equipment (covers also disconnection of tones;
                    exclusively used at the incoming procedures)
                                          }                                     Task
                                          9                                     Spare
                                         10                                     Spare
       ____________________________________________________________________________________________________________________
                                         11                                      {
                          Shall digit analysis be started?
                                          }                                     Decision
                                         12                                     Perform digit analys             Task
       ____________________________________________________________________________________________________________________
                                         13                                      {
               Digit analysis cannot be completed (covers insufficient
              information, waiting for enough digits for routing, etc.)
                                          }                                     Internal input
                                         14                                      {
                      Routing information and service provided
                                          }                                     Internal input
       ____________________________________________________________________________________________________________________
                                         15                                     Unallocated number          Internal input
                                         16                                      {
                Unprovided routing (e.g. transit connection received
                  at an exchange handling termination traffic only)
                                          }                                     Internal input
                                         17                                     Barred routing              Internal input
                                         18                                      {
                           Switching equipment congestion
                                          }                                     Internal input
                                         19                                     Circuit group congesn       Internal input
       ____________________________________________________________________________________________________________________
                                         20                                     Satellite link inclu?          Decision
                                         21                                      {
                    Incoming half-echo suppressor to be included
                                   at distant end?
                                          }                                     Decision
                                         22                                      {
           Transit connection following? (otherwise a terminal connection
                                    is following)
                                          }                                     Decision
                                         23                                     Has Z-digit been reced?        Decision









                                         24                                     Is this the Z-digit?           Decision
       ____________________________________________________________________________________________________________________
                                         31                                      {
                    Perform continuity check at the outgoing end
                     (covers all necessary switching procedures:
                           - connecting of the transceiver
       .ta 1680u 2424u 2832u
                           - disabling of echo suppressors
       .ta 1680u 2424u 2832u
                                - sending check tone
       .ta 1680u 2424u 2832u
                      - automatic reattempts, where applicable)
                                          }                                     Task
                                         32                                      {
            Insert check loop at the incoming end (including disabling of
                                  echo suppressors)
                                          }                                     Task
                                         33                                      {
                     Continuity check OK (covers also receiving
                    of checktone and removal of the transceiver)
                                          }                                     Internal input
                                         34                                      {
            Remove check loop at the incoming end (including enabling of
                                  echo suppressors)
                                          }                                     Task
                                         35                                      {
                           Ignore further register signals
                                          }                                     Task
                                         36                                      {
                  Is continuity check required on outgoing circuit?
                                          }                                     Decision
       ____________________________________________________________________________________________________________________


                                                    Tableau [1T5.608] p.15



                                 H.T. [2T5.608]
                               TABLE A-3 (cont.)



       _____________________________________________________________________________________________
                               No.                                 Designation              Symbol
       _____________________________________________________________________________________________
                               37                            {
         Analyze and store information (received in GSM)
                                }                           Task
                               38                           Access barred               Internal inp                               39                           Digital path not possible   Internal inp                               40                           Store services provided          Task
                               41                           Spare
                               42                            {
                 Additional information required
                                }                           Internal input
                               43                            {
              Set IAM fields as defined by services
                                }                           Task
       _____________________________________________________________________________________________
                               44                            {
        Analyze information requested (applicable to GRQ)
                                }                           Task
                               45                            {
             Is service allowed? (applicable to GRQ)
                                }                           Decision
                               46                            {
          Is information available? (applicable to GRQ)
                                }                           Decision
                               47                            {
          Construct request message (applicable to GRQ)
                                }                           Task
                               48                            {
        Construct information message (applicable to GSM)
                                }                           Task
                               49                           Spare
                               50                           Spare
       _____________________________________________________________________________________________


                                                    Tableau [2T5.608] p.16




 * A.3 :  Explanatory notes on the meanings and uses of SPITEs | see Table
          A-3)

   SPITEs are Switching Processing Interface Telephone Events used in all
three procedures.  For convenience the three signalling procedures are
considered to be processes within a larger switching process and all SPITEs
are considered to be internal to the signalling procedures but having, where
necessary, full access to any switching information provided by other
signalling procedures.  For example digit analysis is initiated by the
incoming procedure, but the results are available to both the interworking and
outgoing procedures, where necessary.  By contrast all FITEs, BITEs and
telephone signals are external signals.  The SPITEs are grouped into three
categories:

   a) SPITEs 1-10 are allocated or reserved for switching SPITEs ;

   b) SPITEs 11-30 are allocated or reserved for digit analysis SPITEs;

   c) SPITEs 31-40 are allocated or reserved for SPITEs used by a restricted
      number of signalling systems .


A.3.1 SPITE 1 activate register function | s used in the incoming procedure to
~~~~~ activate the register function following the receipt of the seizing
signal or the initial address message.  The register function keeps a memory
of all received signals.


A.3.2 SPITE 2 register function activated | s used following SPITE 1 where a
~~~~~ proceed to send signal must be sent.


A.3.3 SPITE 3 deactivate register function | s used in the incoming procedure
~~~~~ to deactivate the register function.  It is used after one of the
following events:

    o clear-forward,

    o register timeout,

    o SPITEs 15-19 (reasons of unsuccessful calls),

    o BITEs 3-17, 19, 20, 27, 28 or any other error condition indicating an
      unsuccessful call.


A.3.4 SPITE 4 set-up speech condition | s used in the incomming procedure to
~~~~~ set-up the speech condition at the end of the register phase.  It is
therefore used in conjunction with SPITE 3 after reception of BITEs 3-7 and
27.

    A.3.4(a) SPITE 4A speech path may be set up , is used in the incoming
             procedure on calls where a BITE 30, has been received in order to
             allow early switchthrough of the speech circuits.


A.3.5 SPITE 5 release speech condition | s used in the incoming or
~~~~~ interworking procedure where a call unsuccessful BITE is received after
SPITE 4.  If the BITE is returned to the incoming procedure, SPITE 5 is used
there but if the BITE is translated to a tone in the interworking procedure
using SPITE 6, then SPITE 5 is used in the interworking procedure.


A.3.6 SPITE 6 return appropriate tone | s used in the incommming procedure
~~~~~ where no electrical signal corresponds to SPITEs 15-19, and also in the
interworking procedure when a BITE is received for which no corresponding BITE
exists in the incoming procedure.


A.3.7 SPITE 7 disconnect tone , is used to disconnect a tone at a point in the
~~~~~ logic procedures other than the release of the call, i.e.  when SPITE 8
is not appropriate.  An example is the disconnection of ringing tone in the
outgoing INMARSAT procedures.


A.3.8 SPITE 8 release all equipment | s used in the incoming procedure when a
~~~~~ clear-forward signal is received after the register phase.


A.3.9 SPITE 11 shall digit analysis be started?  is used in the incoming
~~~~~ procedure to determine, when sufficient digits have been received, that
digit analysis may begin.


A.3.10 SPITE 12 perform digit analysis | s used in the incoming procedure to
~~~~~~ perform digit analysis.  The analysis takes into account the following
information, where available:

    o address information,

    o Z-digit (L- or D-digit),

    o country-code indicator,

    o echo-suppressor indicator,

    o nature-of-circuit indicator,

    o calling-party's-category.

    o service requested.

   SPITE 12 will be followed by one of the SPITEs 13-19 which indicate the
result of the analysis, and are only used in the incoming procedure.


A.3.11 SPITE 13 digit analysis cannot be completed Indicates that insufficient
~~~~~~ address information is available to complete the digit analysis.


A.3.12 SPITE 14 routing information and service provided Indicates that digit
~~~~~~ analysis has been completed and the following information determined:

    o Type of outgoing signalling system,

    o Transit or terminal connection,

    o Echo-suppressor indicator,

    o Nature-of-circuit indicator,

    o Position of Z-digit.

    o Service provided.

    SPITEs 15-19 are results of digit analysis.


A.3.13 SPITE 15 unallocated number Indicates that the received address digits
~~~~~~ represent an unallocated number (country code, area code, etc.).


A.3.14 SPITE 16 unprovided routing | ndicates that the received address digits
~~~~~~ represent a valid code but that the required destination cannot be
reached via this exchange.


A.3.15 SPITE 17 barred routing | ndicates that the received address digits
~~~~~~ represent a valid code but that access to it is barred by reason of,
for example:

    o Wrong calling party's category,

    o Prohibited route-route combination.


A.3.16 SPITE 18 switching equipment congestion Indicates that the switching
~~~~~~ attempt to the outgoing circuit met switching equipment congestion.


A.3.17 SPITE 19 circuit group congestion | ndicates that all circuit groups to
~~~~~~ the required destination were congested.

       SPITEs 20-24 ask for information from the results of digit analysis.


A.3.18 SPITE 20 satellite link included?  is used in the interworking
~~~~~~ procedure to determine the required nature of circuit indicator that
should be transmitted.  This information is available from the results of
digit analysis.


A.3.19 SPITE 21 incoming half-echo-suppressor to be included at distant end?
~~~~~~ is used in the interworking procedure to determine the required echo
suppressor indicator that should be transmitted.  This information is
available from the results of digit analysis.


A.3.20 SPITE 22 transit connection following?  is used in the interworking
~~~~~~ procedure to determine the required country code indicator that should
be transmitted.  This information is available from the results of digit
analysis.


A.3.21 SPITE 23 has Z-digit been received?  is used in the incoming procedure
~~~~~~ following digit analysis to decide whether the Z-digit has already been
received.  The position of the Z-digit is determined as part of the digit
analysis.


A.3.22 SPITE 24 is this the Z-digit?  is used in the incoming procedure to
~~~~~~ decide whether a received register signal is the Z-digit or an address
digit.  This can be determined, since the position of the Z-digit is known
after digit analysis.


A.3.23 SPITE 31 perform continuity check is used in the out going procedure of
~~~~~~ common channel signalling systems to perform the continuity check
including all necessary switching procedures.


A.3.24 SPITE 32 insert check loop is used in the incoming procedure of common
~~~~~~ channel signalling systems to insert the continuity check loop.


A.3.25 SPITE 33 continuity check O.K.  is used in the outgoing procedure of
~~~~~~ common channel signalling systems to indicate a successful continuity
check.


A.3.26 SPITE 34 remove check loop is used in the incoming procedure of common
~~~~~~ channel signalling systems to remove the continuity check loop.


A.3.27 SPITE 35 ignore further register signals is used in the incoming
~~~~~~ procedure of Signalling System No.  5 and R1 following the receipt of
the ST signal to indicate that all further register signals should be ignored.


A.3.28 SPITE 36 is continuity check required on outgoing circuit?  is used in
~~~~~~ conjunction with information received on the incoming link to determine
the continuity check indicator required on the outgoing link.


A.3.29 SPITE 37 analyze and store information is used in the incoming
~~~~~~ procedure on receipt of a General Set-up information Message (GSM).


A.3.30 SPITE 38 access barred indicates that a requested service cannot be
~~~~~~ completed (e.g.  closed user group).


A.3.31 SPITE 39 digital path not possible indicates that a digital path
~~~~~~ cannot be provided.


A.3.32 SPITE 42 additional information required | ndicates that the I/C
~~~~~~ procedure must send a GRQ message.



                                                          Tableau A-4 p.17

                                                          Tableau A-5 p.18

                                                     Tableau A-5 | is p.19

                                                          Tableau A-6 p.20

                                                          Tableau A-7 p.21

                                                          Tableau A-8 p.22

                                                          Tableau A-9 p.23

                                                     Tableau A-9 | is p.24

                                                         Tableau A-10 p.25

                                                         Tableau A-11 p.26





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