Re: [Sipping-emergency] Emergency Scenarios Document

[Tom Taylor <[e-mail]>]

I'll be replying to Henning's comments, but since this note is relatively short I'll
address it first.

McCalmont, Patti wrote:
> Section 3.3
> 
> 
>> In the legacy network ....mapping database.
> 
> 
> The term "mapping database is used a few times within the document. Is mapping
> database trying to refer to a selective routing database that is used to
> determine how to route the call based on the location of the caller to the PSAP?
> If so, a better term would be location database or selective routing database
> (term used in US/Canada. Or, is it trying to refer to the phone number to
> location information, Automatic Location Identification (ALI) database, or both?
> Some clarification is needed.
[PTT]  I'll clarify.  In North American terms I'm referring to the ALI database.

> 
> For PBX operation, an additional issue is that telephone number assignments are
> under control of the private network operator.  PBXs without
> direct-inward-dialing (DID) introduce an additional challenge.  Typically, the
> calling number is used as a unique reference to identify the caller's location.
> 
> Without CAMA or PRI connections for emergency calls, those PBX locations cannot
> convey the caller's identity (even with DID). What is typically used is the
> Billing Number or Main Directory number for the PBX when they don't have the
> CAMA/PRI. There may need some clarification as connections required in order to
> provide the DID stations or is that what was trying to be said with
> "administrative arrangements"?
[PTT] I seem to have gotten this wrong, as you and Henning point out.  I'll have to 
extend the discussion.
> 
> 
> A special arrangement at the switch serving the ECC allows the emergency operator
> to hold open the voice path back to the caller as long as necessary, even if the
> caller goes on-hook.  It should be noted that this functionality is not supported
> for ISDN. Thus, the operator can also ring the caller's line in this situation or
> others where it might be necessary.
> 
> Call Hold applies globally to Basic 911 and is an option for Enhanced 9-1-1 so
> which type of "legacy network" is described in this section. If Enhanced 9-1-1,
> then Call Hold (as stated later) is an optional feature.
> 
> Henning wrote: I would qualify this as "In analog switches, ....". Most switches
> today are effectively ISDN (or equivalent), so this feature is likely only 
> available to a tiny fraction of end systems.
> 
> Most switches today are digital so I don't like the term "analog switches". It
> would be better to talk about the interfaces into the switch as being analog or
> digital (ISDN).

[PTT] Yes, that's right.  In North America, there aren't many ISDN lines, but in 
Europe there are.  In both places, most switches are digital.
> 
> 
> Section 4.3.1
> 
>> There is still the problem of distinguishing between voice and text emergency
>> calls.  If the user enters an actual emergency number, that can be the one that
>> serves the user's needs.  If the configuration is by DHCP or SIP registrar, it
>> may be that selection of the appropriate number is based on pre-configuration
>> of the SIP phone as voice or text bas
> 
> 
> Henning wrote: Unless I'm really off my rocker, the number is the same for TDD
> calls. See http://www.nena.org/PR_Pubs/9-1-1QandA.htm for evidence.
> 
> He is correct. It's the equipment at the PSAP that detects the call as TDD
> nothing in how the user dials.

[PTT] That's in North America.  It's different in Australia.  I suppose I should 
modify the discussion to make it clear that the requirement is only present in some 
countries.

> 
> Patti McCalmont
> 
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