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> In Los Angeles, emergency calls to 911 show up with the caller's address
> and phone number at a CRT.  What kind of set up is used here?

	What you are referring to is generally called Enhanced 911 since it
provides detailed calling party identification, as opposed to plain old 911
which at best only provided a telephone number.
	A 911 call is routed to a special central office trunk circuit, with
such trunk being similar to that of TSPS, in that the trunk (under attendant
control) can hold the calling subscriber seized to the trunk, can re-ring the
line, etc.  This 911 trunk also has available to it the calling number of the
subscriber line which called it; this calling number is sent over a data line
to a telephone company data center which maintains a centralized data dase of
subscriber line numbers against actual name, address, and possibly other
information.  The resultant identity data is then sent back (not necessarily
by the same route) to the public safety organization where the 911 calls are
answered, where it is displayed on a terminal.
	The general trend is to have centralized data bases on a statewide
or LATA-wide basis of subscriber number correlated to name, address, etc.,
rather than to expect the information to reside in the actual central office
where the call originated.  This scheme also quiets some concerns of telephone
company management about potential abuse of information if were too easily
accessed by telephone company personnel; such would be the case if the data
base resided in each central office.
	Most of the Enhanced 911 that has already been implemented has been
done so with technical variations in each installation.  To a certain extent
this is unavoidable, but efforts are being made to standardize the apparatus
and method of installation (at least from the standpoint of AT&T Network
Systems and AT&T Technologies).  One of the great benefits to be derived from
standardization is that Enhanced 911 will eventually be available everywhere,
with calls routed to the PROPER public safety agency for the address of the
calling party; i.e., the telephone company data base will determine to which
public service agency the call should be routed.  Under these circumstances,
a central office will no longer be an arbitrary boundary for the public safety
agency answering 911 calls - which is only proper, since a given central office
will often serve more than one political subdivision. 

==>  Larry Lippman @ Recognition Research Corp., Clarence, New York        <==
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