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==Phrack Inc.==
Volume Two, Issue 24, File 6 of 13
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[] Glossary Terminology []
[] For Enhanced 911 Services []
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[] By The Eavesdropper []
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[] March, 1988 []
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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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