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General Description SSAC15A is an in-band
continuous tone line signalling system used for the transmission
of digit pulses and supervisory signals on bothway inter-PBX
circuits where a suitable DC path is not available. ie Over long
distances.
BASIC SSAC15A CIRCUIT
The system requires a 4-wire presented circuit between the two
PBXs and employs a single tone frequency of 2280 Hz for
signalling in each direction of transmission. When the circuit is
in an idle state the 2280 Hz signalling tone is continously
present in both directions of transmission and therefore the
SSAC15A is described as a Tone-on-Idle system.
Note
Low Level Tone is a tone sent at -20 dBm0
High Level Tone is a tone sent at -10 dBm0
Terminating Equipment
On modern electronic PBXs that support AC15A it is normal to
simply terminate the 4 wire circuit onto an AC15A interface card
which slots directly into the appropriate position in the PBX. On
older PABXs or electronic PABXs/CCSs that do not support AC15A it
is normal to terminate the 4 wire circuit onto a signalling unit
which provides an AC15A to DC5 (E&M) conversion.
Transmission Requirements
The signal frequency is transmitted to line at two standard
levels: -10 dBm0 (High Level) and -20 dDm0 (Low Level). The
signal receiver has the same sensitivity in each case. It will
accept signal levels in the range: -3 dBm to -29 dBm.
Note:- Level measurements should be made on Transmit and Receive
of the 4 wire.
Fault Symptoms
If the 'transmit' pair is disconnected, the trunk at the distant
PBX will be PG. PBX calls at the local end will fail.
Monitoring of Circuit
Listen on transmit and receive pairs for 'Tone on Idle' signal.
You will need a high impedance telephone or other suitable
listening device. This is a quick check to see whether a tone is
being sent from the local end on the transmit pair and being
received from the distant end on the receive pair.
Using this method you may also monitor signalling tones being
sent when circut is in use.
To prove the level of these tones you will need a LMS.
Loop back test
Using a suitable Patching cord connect the transmit and receive
at the local end together. Ensure that the line is totally
disconnected from the distant end. If the circiut goes normal
then the local end is ok.
If two circuits are available then these can be connected
together (ensuring all distant ends are disconnected). The two
circuits should go idle and calls should be able to be made in
and out of the local end.
General Description SSAC15B is the preferred
method of inter-PBX signalling on circuits over any 4 wire
presented transmission path where SSMF5 inter-register signalling
is employed.
Transmission Requirements
Transmission requirements are as described in SSAC15A section.
Methods of Testing The methods of testing are
the same as those described in the AC15A section.
AC15C
General Description SSAC15C is used to
provide external extension and out of area exchange line
signalling with recall facilities. Signalling Units 53A and 54A
are used. For description of circuits refer to Signaling Units
53A and 54A.
General Description SSAC15D is an in-band
signalling system used on International inter-PBX circuits or
appropriate inland inter- PBX circuits. It uses a single
frequency of 2280 Hz in each direction of a 4 wire transmission
path.
Transmission Requirements
Transmission Requirements are as described in SSAC15A section.
Methods of Testing Circuits
The methods used tor testing a SSAC15D circuit are the same as
those described in the SSAC15A section