A few definitions and concepts:
Definition of E911
"911" has been designated in the United
States as the number to be used by the public to summons emergency aid
or to report a crime, fire or accident. Its main purpose is to make it
easier for people in time of emotional stress to contact the proper
emergency agency. An important advantage of 911 emergency service is
improved (reduced) response time.
Purpose of a E911
The purpose
of Enhanced 9-1-1 systems is to connect a caller with an emergency to
the correct responding agency. Current Enhanced 9-1-1 systems consist of
three separate elements: the Network Element, the Public Safety
Answering Point (PSAP) Element and the Data Management System/Automatic
Location Identification (DMS/ALI) Element. The digits 9-1-1 provide the
public direct access to the E 9-1-1 system.
Public Service
Access Point (PSAP)
The PSAP
is the designated agency that receives E 9-1-1 calls and, through the
efforts of the PSAP telecommunicator, alerts the proper emergency
response agencies (i.e., fire, police, ambulance). The traditional PSAP
may receive the ANI information from the control tandem and, in a
conventional configuration, will interface with the DMS/ALI database
through dedicated data links from the PSAP. Digital ISDN PSAPS may
receive ANI and ALI information from the subtending serving telephone
exchange or other switching element. The Street address and other
subscriber information from the ALI database, along with the callers ANI
and emergency service information, is displayed at the attendant's
position.
Rural Addressing
System
A Rural Addressing System promotes the
orderly development of the county and to better locate residences,
businesses, and other buildings in the region/County. The lack of
permanent location-type addresses can result in lost time and increased
expenses by utility companies, governmental agencies, county fire and
sheriff departments, delivery and repair companies. Worst of all, it
could result in lost lives by the inability of emergency services to
find rural residents.
Telephone Number (TN) Database
The TN database contains all the out-dial
subscriber lines within the exchanges in the county / city . This
information includes the individual telephone number, name, address,
location (apartment, lot, etc.) and class and type of service. The TN
database is necessary to support the ALI retrieval to be displayed at
the PSAP.
It is initially created from an extract
of customer account data by each Telco, then processed against the MSAG.
All subscriber lines find an exact match and are assigned the
appropriate ESN. Any discrepancies will be resolved by the Telco and the
County / City.
The TN database is updated by processing
daily service orders against the MSAG. Options for providing this data
to INTRADO is explained in detail later in this document.
E911 Call Flow
The following steps are involved in the E911 emergency call process.
STEP ACTION
1.
The county resident requires emergency
aid and dials 911.
2.
The digits are received in the central
office serving the exchange from which the user is dialing.
3.
The central office sends the ANI
(Automatic Number Identification) to the 911 tandem office.
4.
The tandem office finds the associated
ESN for the calling telephone number via the TN/ESN table.
5.
Based on the ESN, the call is switched,
via a dedicated trunk, to the appropriate PSAP.
6.
The calling number is displayed (ANI) at
the PSAP.
7.
The ANI information is sent to the
primary and secondary ALI processors for retrieval.
8.
The primary or secondary ALI (Automatic
Location Information) computer retrieves the ALI data from the database.
9.The
ALI computer returns the ALI to the PSAP.
10.
The data is received at the PSAP and the information is displayed.
11.
The PSAP attendant verifies the telephone number and the street address
that has appeared on the screen and obtains information as to which
emergency service is needed. The attendant then depresses the button
corresponding to the agency requested, e.g., fire or ambulance (one
button transfer feature) the call is automatically transferred.
12.
The details for each call (calling
number, answering attendant’s number, time of answer, time of transfer
and / or disconnect and the trunk number) are printed after disconnect
on a printer at the PSAP.
13.
The agency receives the call and a display of the caller’s telephone
number, name and street address (optional equipment). The PSAP
attendant may remain on the line as long as necessary.
14.
The agency then dispatches an emergency unit to the caller’s address.
