Subject: RE: [Ecrit] Timing of PSAPs changing coverage areas

From: "Tim Dunn" <[email-masked]>
Date: Tue, 20 Sep 2005 15:34:01 -0600

James-

In certain parts of the US (generally rural, but I think there are also some
urban examples), I am aware of local police departments that answer their
emergency calls between 8am and 5pm.  At other times the calls are routed to
a county or state level center that is a 24x7 operation.  So the answer to
your question would be that routing changes can occur daily in some places.

In the legacy circuit switched environment, there is generally a way to busy
out the inbound emergency trunks, allowing for routing of calls to another
location.  In my example above, the local PSAP throws a switch and the calls
now route to an alternate location.  

This is also, in general, how trunk busyouts occur if a PSAP needs to
quickly vacate and you want the calls routed elsewhere.  My experience was
that there were switches at the PSAP, at the central office (to busy out the
trunks) and sometimes at a local backup PSAP (unbusying those trunks to
begin accepting calls).  If you had your primary and backup location out of
business, there are switch level instructions on where to route.

Tim Dunn

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
James M. Polk
Sent: Tuesday, September 20, 2005 2:56 PM
To: [email-masked]
Subject: [Ecrit] Timing of PSAPs changing coverage areas

All

I've heard and read the statements and requirements from folks that the 
routing of a call to a PSAP needs to be as fresh as possible because a 
particular PSAP might have moved, or more accurately, that a location might 
be served "on a moment's notice" by a different PSAP.

I'd like to ask how often this happens today. Does anyone know how often a 
location needs to contact a different PSAP than its normal/standard one?

It seems to me that a lot of us might be imagining a worse-case scenario 
that we need to design protocols for, and that this worse-case scenario 
happens often. If this is, say only 0.01% of the time - or even under 5% of 
all emergency calls (2 standard deviations, or SDs), I'm thinking we're 
focusing too much energy on solving something that is a statistical
"outlier".

Today's emergency systems aren't build for 2 SDs, and especially not for 4
SDs.

cheers,
James

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---

From: "James M. Polk" <[email-masked]>
Date: Tue, 20 Sep 2005 23:33:12 -0500

Tim

This is a good example, and one that SIP covers already, as time-of-day 
routing is a piece of cake to a SIP Proxy.

cheers,
James

                                 *******************

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From: Nate Wilcox <[email-masked]>
Date: Fri, 23 Sep 2005 16:08:19 -0400

Sorry I did not pick up on this thread sooner. As a former PSAP type person
I can tell you that in the State of Vermont over the last 7 years we have
had 5 significant PSAP reconfigurations that involved re-routing of calls to
new permanent locations. However, using historical references to determine
this is not going to help. Their is a shift afoot right now towards
dispatch/PSAP consolidation and the rate of change could increase
exponentially particularly as new funding mechanisms in pursuit of better
disaster preparedness becomes available for this specific purpose. I would
also add that bringing new PSAP's on line and decommisioing old ones will
become more common place as old cumbersome legacy gear gets replaced by more
capable, less complex systems.
 Nate Wilcox