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TUCoPS :: Phreaking Technical System Info :: 911.txt

The original E911 document (the one that started it all)





[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]
[]                                                        []
[]              Control Office Administration             []
[]              Of Enhanced 911 Services For              []
[]       Special Services And Major Account Centers       []
[]                                                        []
[]                   By The Eavesdropper                  []
[]                                                        []
[]                       March, 1988                      []
[]                                                        []
[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]


Description of Service
~~~~~~~~~~~~~~~~~~~~~~
  The control office for Emergency 911 service is assigned in accordance with
the existing standard guidelines to one of the following centers:

   o  Special Services Center (SSC)      o  Major Accounts Center (MAC)
   o  Serving Test Center (STC)          o  Toll Control Center (TCC)

The SSC/MAC designation is used in this document interchangeably for any of
these four centers.  The Special Services Centers (SSCs) or Major Account
Centers (MACs) have been designated as the trouble reporting contact for all
E911 customer (PSAP) reported troubles.  Subscribers who have trouble on an
E911 call will continue to contact local repair service (CRSAB) who will refer
the trouble to the SSC/MAC, when appropriate.

Due to the critical nature of E911 service, the control and timely repair of
troubles is demanded.  As the primary E911 customer contact, the SSC/MAC is in
the unique position to monitor the status of the trouble and insure its
resolution.

System Overview
~~~~~~~~~~~~~~~
  The number 911 is intended as a nationwide universal telephone number which
provides the public with direct access to a Public Safety Answering Point
(PSAP).  A PSAP is also referred to as an Emergency Service Bureau (ESB).  A
PSAP is an agency or facility which is authorized by a municipality to receive
and respond to police, fire and/or ambulance services.  One or more attendants
are located at the PSAP facilities to receive and handle calls of an emergency
nature in accordance with the local municipal requirements.

An important advantage of E911 emergency service is improved (reduced) response
times for emergency services.  Also close coordination among agencies providing
various emergency services is a valuable capability provided by E911 service.

1A ESS is used as the tandem office for the E911 network to route all 911 calls
to the correct (primary) PSAP designated to serve the calling station.  The
E911 feature was developed primarily to provide routing to the correct PSAP for
all 911 calls.  Selective routing allows a 911 call originated from a
particular station located in a particular district, zone, or town, to be
routed to the primary PSAP designated to serve that customer station regardless
of wire center boundaries.  Thus, selective routing eliminates the problem of
wire center boundaries not coinciding with district or other political
boundaries.

The services available with the E911 feature include:

      Forced Disconnect         Default Routing
      Alternative Routing       Night Service
      Selective Routing         Automatic Number Id entification (ANI)
      Selective Transfer        Automatic Location Identification (ALI)


Preservice/Installation Guidelines
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   When a contract for an E911 system has been signed, it is the responsibility
of Network Marketing to establish an implementation/cutover committee which
should include a representative from the SSC/MAC.  Duties of the E911
Implementation Team include coordination of all phases of the E911 system
deployment and the formation of an on-going E911 maintenance subcommittee.

Marketing is responsible for providing the following customer specific
information to the SSC/MAC prior to the start of call through testing:

 o  All PSAP's (name, address, local contact)
 o  All PSAP circuit ID's
 o  1004 911 service request including PSAP details on each PSAP
    (1004 Section  K, L, M)
 o  Network configuration
 o  Any vendor information (name, telephone number, equipment)

The SSC/MAC needs to know if the equipment and sets at the PSAP are maintained
by the BOCs, an independent company, or an outside vendor, or any combination.
This information is then entered on the PSAP profile sheets and reviewed
quarterly for changes, additions and deletions.

Marketing will secure the Major Account Number (MAN) and provide this number to
Corporate Communications so that the initial issue of the service orders carry
the MAN and can be tracked by the SSC/MAC via CORDNET.  PSAP circuits are
official services by definition.

All service orders required for the installation of the E911 system should
include the MAN assigned to the city/county which has purchased the system.

In accordance with the basic SSC/MAC strategy for provisioning, the SSC/MAC
will be Overall Control Office (OCO) for all Node to PSAP circuits (official
services) and any other services for this customer.  Training must be scheduled
for all SSC/MAC involved personnel during the pre-service stage of the project.

The E911 Implementation Team will form the on-going maintenance subcommittee
prior to the initial implementation of the E911 system.  This sub-committee
will establish post implementation quality assurance procedures to ensure that
the E911 system continues to provide quality service to the customer.
Customer/Company training, trouble reporting interfaces for the customer,
telephone company and any involved independent telephone companies needs to be
addressed and implemented prior to E911 cutover.  These functions can be best
addressed by the formation of a sub-committee of the E911 Implementation Team
to set up guidelines for and to secure service commitments of interfacing
organizations.  A SSC/MAC supervisor should chair this subcommittee and include
the following organizations:

1) Switching Control Center
      - E911 translations
      - Trunking
      - End office and Tandem office hardware/software
2) Recent Change Memory Administration Center
      - Daily RC update activity for TN/ESN translations
      - Processes validity errors and rejects 3) Line and Number Administration
      - Verification of TN/ESN translations 4) Special Service Center/Major
        Account Center
      - Single point of contact for all PSAP and Node to host troubles
      - Logs, tracks & statusing of all trouble reports
      - Trouble referral, follow up, and escalation
      - Customer notification of status and restoration
      - Analyzation of "chronic" troubles
      - Testing, installation and maintenance of E911 circuits 5) Installation
        and Maintenance (SSIM/I&M)
     - Repair and maintenance of PSAP equipment and Telco owned sets 6)
       Minicomputer Maintenance Operations Center
     - E911 circuit maintenance (where applicable) 7) Area Maintenance Engineer
     - Technical assistance on voice (CO-PSAP) network related E911 troubles


Maintenance Guidelines
~~~~~~~~~~~~~~~~~~~~~~
  The CCNC will test the Node circuit from the 202T at the Host site to the
202T at the Node site.  Since Host to Node (CCNC to MMOC) circuits are official
company services, the CCNC will refer all Node circuit troubles to the SSC/MAC.
The SSC/MAC is responsible for the testing and follow up to restoration of
these circuit troubles.

Although Node to PSAP circuit are official services, the MMOC will refer PSAP
circuit troubles to the appropriate SSC/MAC.  The SSC/MAC is responsible for
testing and follow up to restoration of PSAP circuit troubles.

The SSC/MAC will also receive reports from CRSAB/IMC(s) on subscriber 911
troubles when they are not line troubles.  The SSC/MAC is responsible for
testing and restoration of these troubles.

Maintenance responsibilities are as follows:

SCC*            Voice Network (ANI to PSAP)                 *SCC responsible
for tandem switch SSIM/I&M        PSAP Equipment (Modems, CIU's, sets)
Vendor          PSAP Equipment (when CPE) SSC/MAC         PSAP to Node
circuits, and tandem to PSAP voice circuits (EMNT) MMOC            Node site
(Modems, cables, etc)

Note:  All above work groups are required to resolve troubles by
interfacing        with appropriate work groups for resolution.

The Switching Control Center (SCC) is responsible for E911/1AESS translations
in tandem central offices.  These translations route E911 calls, selective
transfer, default routing, speed calling, etc., for each PSAP.  The SCC is also
responsible for troubleshooting on the voice network (call originating to end
office tandem equipment).

For example, ANI failures in the originating offices would be a responsibility
of the SCC.

Recent Change Memory Administration Center (RCMAC) performs the daily tandem
translation updates (recent change) for routing of individual telephone
numbers.

Recent changes are generated from service order activity (new service, address
changes, etc.) and compiled into a daily file by the E911 Center (ALI/DMS E911
Computer).

SSIM/I&M is responsible for the installation and repair of PSAP equipment. PSAP
equipment includes ANI Controller, ALI Controller, data sets, cables, sets, and
other peripheral equipment that is not vendor owned.  SSIM/I&M is responsible
for establishing maintenance test kits, complete with spare parts for PSAP
maintenance.  This includes test gear, data sets, and ANI/ALI Controller parts.

Special Services Center (SSC) or Major Account Center (MAC) serves as the
trouble reporting contact for all (PSAP) troubles reported by customer.  The
SSC/MAC refers troubles to proper organizations for handling and tracks status
of troubles, escalating when necessary.  The SSC/MAC will close out troubles
with customer.  The SSC/MAC will analyze all troubles and tracks "chronic" PSAP
troubles.

Corporate Communications Network Center (CCNC) will test and refer troubles on
all node to host circuits.  All E911 circuits are classified as official
company property.

The Minicomputer Maintenance Operations Center (MMOC) maintains the E911
(ALI/DMS) computer hardware at the Host site.  This MMOC is also responsible
for monitoring the system and reporting certain PSAP and system problems to the
local MMOC's, SCC's or SSC/MAC's.  The MMOC personnel also operate software
programs that maintain the TN data base under the direction of the E911 Center.
The maintenance of the NODE computer (the interface between the PSAP and the
ALI/DMS computer) is a function of the MMOC at the NODE site.  The MMOC's at
the NODE sites may also be involved in the testing of NODE to Host circuits.
The MMOC will also assist on Host to PSAP and data network related troubles not
resolved through standard trouble clearing procedures.

Installation And Maintenance Center (IMC) is responsible for referral of E911
subscriber troubles that are not subscriber line problems.

E911 Center - Performs the role of System Administration and is responsible for
overall operation of the E911 computer software.  The E911 Center does A-Z
trouble analysis and provides statistical information on the performance of the
system.

This analysis includes processing PSAP inquiries (trouble reports) and referral
of network troubles.  The E911 Center also performs daily processing of tandem
recent change and provides information to the RCMAC for tandem input.  The E911
Center is responsible for daily processing of the ALI/DMS computer data base
and provides error files, etc. to the Customer Services department for
investigation and correction.  The E911 Center participates in all system
implementations and on-going maintenance effort and assists in the development
of procedures, training and education of information to all groups.

Any group receiving a 911 trouble from the SSC/MAC should close out the trouble
with the SSC/MAC or provide a status if the trouble has been referred to
another group.  This will allow the SSC/MAC to provide a status back to the
customer or escalate as appropriate.

Any group receiving a trouble from the Host site (MMOC or CCNC) should close
the trouble back to that group.

The MMOC should notify the appropriate SSC/MAC when the Host, Node, or all Node
circuits are down so that the SSC/MAC can reply to customer reports that may be
called in by the PSAPs.  This will eliminate duplicate reporting of troubles.
On complete outages the MMOC will follow escalation procedures for a Node after
two (2) hours and for a PSAP after four (4) hours.  Additionally the MMOC will
notify the appropriate SSC/MAC when the Host, Node, or all Node circuits are
down.

The PSAP will call the SSC/MAC to report E911 troubles.  The person reporting
the E911 trouble may not have a circuit I.D. and will therefore report the PSAP
name and address.  Many PSAP troubles are not circuit specific.  In those
instances where the caller cannot provide a circuit I.D., the SSC/MAC will be
required to determine the circuit I.D. using the PSAP profile.  Under no
circumstances will the SSC/MAC Center refuse to take the trouble.  The E911
trouble should be handled as quickly as possible, with the SSC/MAC providing as
much assistance as possible while taking the trouble report from the caller.

The SSC/MAC will screen/test the trouble to determine the appropriate handoff
organization based on the following criteria:

    PSAP equipment problem:  SSIM/I&M     Circuit problem:  SSC/MAC     Voice
network problem:  SCC (report trunk group number)     Problem affecting
multiple PSAPs (No ALI report from all PSAPs):
Contact                                      the MMOC to check for NODE or
Host                                      computer problems before further
testing.

The SSC/MAC will track the status of reported troubles and escalate as
appropriate.  The SSC/MAC will close out customer/company reports with the
initiating contact.  Groups with specific maintenance responsibilities, defined
above, will investigate "chronic" troubles upon request from the SSC/MAC and
the ongoing maintenance subcommittee.

All "out of service" E911 troubles are priority one type reports.  One link
down to a PSAP is considered a priority one trouble and should be handled as if
the PSAP was isolated.

The PSAP will report troubles with the ANI controller, ALI controller or set
equipment to the SSC/MAC.

NO ANI:  Where the PSAP reports NO ANI (digital display screen is blank) ask if
this condition exists on all screens and on all calls.  It is important to
differentiate between blank screens and screens displaying 911-00XX, or all
zeroes.

When the PSAP reports all screens on all calls, ask if there is any voice
contact with callers.  If there is no voice contact the trouble should be
referred to the SCC immediately since 911 calls are not getting through which
may require alternate routing of calls to another PSAP.

When the PSAP reports this condition on all screens but not all calls and has
voice contact with callers, the report should be referred to SSIM/I&M for
dispatch.  The SSC/MAC should verify with the SCC that ANI is pulsing before
dispatching SSIM.

When the PSAP reports this condition on one screen for all calls (others work
fine) the trouble should be referred to SSIM/I&M for dispatch, because the
trouble is isolated to one piece of equipment at the customer premise.

An ANI failure (i.e. all zeroes) indicates that the ANI has not been received
by the PSAP from the tandem office or was lost by the PSAP ANI controller.  The
PSAP may receive "02" alarms which can be caused by the ANI controller logging
more than three all zero failures on the same trunk.  The PSAP has been
instructed to report this condition to the SSC/MAC since it could indicate an
equipment trouble at the PSAP which might be affecting all subscribers calling
into the PSAP.  When all zeroes are being received on all calls or "02" alarms
continue, a tester should analyze the condition to determine the appropriate
action to be taken.  The tester must perform cooperative testing with the SCC
when there appears to be a problem on the Tandem-PSAP trunks before requesting
dispatch.

When an occasional all zero condition is reported, the SSC/MAC should dispatch
SSIM/I&M to routine equipment on a "chronic" troublesweep.

The PSAPs are instructed to report incidental ANI failures to the BOC on a PSAP
inquiry trouble ticket (paper) that is sent to the Customer Services E911 group
and forwarded to E911 center when required.  This usually involves only a
particular telephone number and is not a condition that would require a report
to the SSC/MAC.  Multiple ANI failures which our from the same end office (XX
denotes end office), indicate a hard trouble condition may exist in the end
office or end office tandem trunks.  The PSAP will report this type of
condition to the SSC/MAC and the SSC/MAC should refer the report to the SCC
responsible for the tandem office.  NOTE: XX is the ESCO (Emergency Service
Number) associated with the incoming 911 trunks into the tandem.  It is
important that the C/MAC tell the SCC what is displayed at the PSAP (i.e.
911-0011) which indicates to the SCC which end office is in trouble.

Note:  It is essential that the PSAP fill out inquiry form on every ANI
failure.

The PSAP will report a trouble any time an address is not received on an
address display (screen blank) E911 call.  (If a record is not in the 911 data
base or an ANI failure is encountered, the screen will provide a display
noticing such condition).  The SSC/MAC should verify with the PSAP whether the
NO ALI condition is on one screen or all screens.

When the condition is on one screen (other screens receive ALI information) the
SSC/MAC will request SSIM/I&M to dispatch.

If no screens are receiving ALI information, there is usually a circuit trouble
between the PSAP and the Host computer.  The SSC/MAC should test the trouble
and refer for restoral.

Note:  If the SSC/MAC receives calls from multiple PSAP's, all of which
are receiving NO ALI, there is a problem with the Node or Node to Host
circuits or the Host computer itself.  Before referring the trouble the
SSC/MAC should call the MMOC to inquire if the Node or Host is in
trouble.

Alarm conditions on the ANI controller digital display at the PSAP are to be
reported by the PSAP's.  These alarms can indicate various trouble conditions
o so the SSC/MAC should ask the PSAP if any portion of the E911 system is not
functioning properly.

The SSC/MAC should verify with the PSAP attendant that the equipment's primary
function is answering E911 calls.  If it is, the SSC/MAC should request a
dispatch SSIM/I&M.  If the equipment is not primarily used for E911, then the
SSC/MAC should advise PSAP to contact their CPE vendor.

Note:  These troubles can be quite confusing when the PSAP has vendor
equipment mixed in with equipment that the BOC maintains.  The
Marketing representative should provide the SSC/MAC information
concerning any unusual or exception items where the PSAP should contact
their vendor. This information should be included in the PSAP profile
sheets.

ANI or ALI controller down:  When the host computer sees the PSAP equipment
down and it does not come back up, the MMOC will report the trouble to the
SSC/MAC; the equipment is down at the PSAP, a dispatch will be required.

PSAP link (circuit) down:  The MMOC will provide the SSC/MAC with the circuit
ID that the Host computer indicates in trouble.  Although each PSAP has two
circuits, when either circuit is down the condition must be treated as an
emergency since failure of the second circuit will cause the PSAP to be
isolated.

Any problems that the MMOC identifies from the Node location to the Host
computer will be handled directly with the appropriate MMOC(s)/CCNC.

Note:  The customer will call only when a problem is apparent to the
PSAP. When only one circuit is down to the PSAP, the customer may not be
aware there is a trouble, even though there is one link down,
notification should appear on the PSAP screen.  Troubles called into the
SSC/MAC from the MMOC or other company employee should not be closed out
by calling the PSAP since it may result in the customer responding that
they do not have a trouble.  These reports can only be closed out by
receiving information that the trouble was fixed and by checking with
the company employee that reported the trouble.  The MMOC personnel will
be able to verify that the trouble has cleared by reviewing a printout
from the host.

When the CRSAB receives a subscriber complaint (i.e., cannot dial 911) the RSA
should obtain as much information as possible while the customer is on the
line.

For example, what happened when the subscriber dialed 911?  The report is
automatically directed to the IMC for subscriber line testing.  When no line
trouble is found, the IMC will refer the trouble condition to the SSC/MAC.  The
SSC/MAC will contact Customer Services E911 Group and verify that the
subscriber should be able to call 911 and obtain the ESN.  The SSC/MAC will
verify the ESN via 2SCCS.  When both verifications match, the SSC/MAC will
refer the report to the SCC responsible for the 911 tandem office for
investigation and resolution.  The MAC is responsible for tracking the trouble
and informing the IMC when it is resolved.


For more information, please refer to E911 Glossary of Terms.
_______________________________________________________________________________

                                ==Phrack Inc.==

                      Volume Two, Issue 24, File 6 of 13

[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]
[]                                                        []
[]                  Glossary Terminology                  []
[]                For Enhanced 911 Services               []
[]                                                        []
[]                   By The Eavesdropper                  []
[]                                                        []
[]                       March, 1988                      []
[]                                                        []
[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]

E911 - Enhanced 911:  Features available include selective routing,
selective transfer, fixed transfer, alternate routing, default routing,
Automatic Number Display, Automatic Location Identification, night
service, default routing, call detail record.

End Office - Telephone central office which provides dial tone to the
             subscriber calling 911. The "end office" provides ANI
             (Automatic Number Identification) to the tandem office.

Tandem Office
 - Telephone central office which serves as a tandem (or hub) for all
911 calls.  Must be a 1AESS type of central office. The tandem office
translations contain the TN/ESN relationships which route the 911 call
to the proper SAP.  The tandem office looks up the ANI (TN) that it
receives from the end office and finds the ESN (routing information)
which corresponds to a seven digit number ringing in at a PSAP.

PSAP - Public Safety Answering Point, usually the police, fire and/or
rescue groups as determined by the local municipalities.  A "ringin"
will not have ANI or ALI capabilities, but just receives calls or
transferred calls from another PSAP.

ESN - Emergency Service Number (XXX) that is assigned to the
subscriber's telephone number in the tandem office translations The ESN
represents a seven digit number by which the tandem office routes the
call to the proper PSAP.  PSAPs with ALI capabilities also receive a
display of the ESN information which shows which police, fire and rescue
agency serves the telephone number calling 911.  An ESN is a unique
combination of police, fire, and rescue service for purposes of routing
the E911 call.

ANI - Automatic Number Identification corresponds to the subscriber's
seven digit telephone number.  The ANI displays at the PSAP on the
digital ANI display console.

ALI - Automatic Location Identification provides for an address display
of the subscriber calling 911.  With ALI, the PSAP receives the ANI
display and an ALI display on a screen.  The ALI display includes the
subscriber's address, community, state, type of service and if a
business, the name of the business.  The PSAP will also get a display of
the associated ESN information (police, fire, rescue).

Selective Routing - The capability to route a call to the particular
PSAP serving the address associated with the TN making the 911 call.
Selective routing is achieved by building TN/ESN translations in the
tandem central office. These translations are driven by the E911 data
base which assigns the ESN to each telephone number based on the
customer's address.  Service order activity keeps the E911 data base
updated.  The E911 data base, in turn, generates recent change to the
tandem office (through the SCC or RCMAC) to update the TN/ESN
translations in the tandem data base.

Selective Transfer - Provides the PSAP with the ability to transfer the
incoming 911 call to a fire or rescue service for the particular number
calling 911 by pushing one button for fire or rescue.  For example, if
an incoming 911 call was reporting a fire, the PSAP operator would push
the fire button on the ANI console; the call would go back to the tandem
office, do a lookup for the seven digit number associated with fire
department, for the ESN assigned to the calling TN, and automatically
route the call to that fire department.  This differs from "fixed"
transfer which routes every call to the same fire or rescue number
whenever the fire or rescue button is pushed.  The PSAP equipment is
optioned to provide either fixed or selective transfer capabilities.

Alternate Routing - Alternate routing provides for a predetermined
routing for 911 calls when the tandem office is unable to route the
calls over the 911 trunks for a particular PSAP due to troubles or all
trunks busy.

Default Routing - Provides for routing of 911 calls when there is an ANI
failure.  The call will be routed to the "default" ESN associated with
the he NNX the caller is calling from. Default ESNs are preassigned in
translations and are usually the predominant ESN for a given wire
center.

Night Service - Night service works the same as alternate routing in
that the calls coming into a given PSAP will automatically be routed to
another preset PSAP when all trunks are made busy due to the PSAP
closing down for the night.

Call Detail Record - When the 911 call is terminated by the PSAP
operator, the ANI will automatically print-out on the teletypewriter
located at the PSAP.  The printout will contain the time the call came
into the PSAP, the time it was picked up by an operator, the operator
number, the time the call was transferred, if applicable, the time the
call was terminated and the trunk group number associated with the call.
Printouts of the ALI display are now also available, if the PSAP has
purchased the required equipment.

ANI Failure - Failure of the end office to identify the call and provide
the ANI (telephone number) to the tandem office; or, an ANI failure
between the tandem office and the PSAP.

Misroute - Any condition that results in the 911 call going to the wrong
PSAP. A call can be misrouted if the ESN and associated routing
information are incorrect in the E911 data base and/or tandem data base.
A call can also be misrouted if the call is an ANI failure, which
automatically default routes.

Anonymous Call - If a subscriber misdials and dials the seven digit
number associated with the PSAP position, they will come in direct and
ANI display as 911-0000 which will ALI as an anonymous call.  The seven
digit numbers associated with the PSAP positions are not published even
to the PSAPs.

Spurious 911 Call - Occasionally, the PSAP will get a call that is not
associated with a subscriber dialing 911 for an emergency. It could be a
subscriber who has not dialed 911, but is dialing another number, or has
just picked up their phone and was connected with the PSAP.  These
problems are equipment related, particularly when the calls originate
from electromechanical or step by step offices, and are reported by the
E911 Center to Network Operations upon receipt of the PSAP inquiry
reporting the trouble. The PSAP may get a call and no one is there; if
they call the number back, the number may be disconnected or no one
home. Again these are network troubles and must be investigated.
Cordless telephones can also generate "spurious" calls in to the PSAPs.
Generally, the PSAP will hear conversation on the line, but the
subscribers are not calling 911.  The PSAP may report spurious calls to
to repair if they become bothersome, for example, the same number
ringing in continually.

No Displays - A condition where the PSAP ALI display screen is blank.
This type of trouble should be reported immediately to the SSC/MAC. If
all screens at the PSAP are blank, it is an indication that the problem
is in the circuits from the PSAP to the E911 computer.  If more than one
PSAP is experiencing no display, it may be a problem with the Node
computer or the E911 computer. The SSC/MAC should contact the MMOC to
determine the health of the HOST computer.

Record Not Found - If the host computer is unable to do a look up on a
given ANI request from the PSAP, it will forward a Record Not Found
message to the PSA ALI screen.  This is caused by service order activity
for a given subscriber not being processed into the E911 data base, or
HOST computer system problems whereby the record cannot be accessed at
that point in time.

No ANI - This condition means the PSAP received a call, but no telephone
number displayed on the ANI console.  The PSAP should report this
condition immediately to the SSC/MAC.

PSAP Not Receiving Calls - If a PSAP cannot receive calls or request
retrievals from the E911 host computer, i.e., cable cut, the calls into
that PSAP must be rerouted to another PSAP.  The Switching Control
Center must be notified to reroute the calls in the tandem office E911
translations.

MSAG - Master Street Address Guide.  The MSAG ledgers are controlled by
the municipality which has purchased the E911 ALI service, in that they
assign which police, fire or rescue agency will serve a given street and
number range.  They do this by assigning an ESN to each street range,
odd, even, community that is populated in the county or municipality
served.  These MSAGs are then used as a filter for service order
activity into the E911 computer data base to assign ESNs to individual
TN records.  This insures that each customer will be routed to the
correct agency for their particular address.  In a non-ALI County, TAR
codes are used by the Telephone company to assign ESNs to service
conductivity and the County does not control the ESN assignment.  TAR
codes represent the taxing authority for the given subscriber which
should correspond to their police, fire and rescue agencies.  The MG
method, of course, is more accurate because it is using the actual
service address of the customer to route the call and provides the
county with more flexibility in assigning fire and rescue district, etc.
The Customer Services E911 Group maintains the E911 computer data base
and interfaces with the County (customer) on all MSAG or data base
activity.
_______________________________________________________________________________



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