[Asterisk-Users] 911 context, is this right?

[Adam Goryachev]

On Mon, 2005-06-06 at 07:17 -0400, Andrew Kohlsmith wrote:
> On Friday 03 June 2005 05:50, Chris Coulthurst wrote:
> > I have 3 analog trunks zap/1, zap/4 and zap/5.  zap/5 is the least used
> > line.  Would the following work for 911 calls?
> Why would you do this?  Use a group:

Yes, use a group... but...

> zaptel.conf:
> group = 9
> channel => 1,4,5
> 
> [e911]
> exten => 911,1,Dial(Zap/g9/ww911)
> exten => 911,102,SoftHangup(Zap/5)
> exten => 911,103,Goto(1)

Boom, you just hungup on the emergency call that was already in
progress.... I wouldn't call that even close to ideal. PS, you might at
least somehow randomise the line you will hangup on...

> Basically dial using the first free line in group 9.  If the Dial fails, hang 
> up zap/5 and try again.  I added two 'w's in the dial string just to make 
> sure the telco switch is ready to receive DTMF (this may not be necessary)

This will delay the call being sent, with absolutely no feedback to the
caller.

> I'm not checking other lines than 5 (there's an assumption that line 5 is 
> always going to work but in an emergency situation I'd just as soon soft 
> hangup all 3 channels and try again.  

Yes, line 5 may not work, and also line 5 is more likely to have another
emergency call in progress. I disagree with hanging up channels in this
manner... IMHO, it is worse to hangup an emergency call in-progress than
to simply return congestion.... You must check that the call in progress
isn't itself an emergency call.

> I also *TOTALLY* disagree with using Ringing() to calm the caller.  If the 
> call's not going through they SHOULD be thinking of using an alternative way 
> to reach 911, not calmly waiting for an answer that just wont come.

But the call *IS* going through, I just allowed the caller to hear
ringing for 2 seconds instead of dead-air. We just made a line available
for him, so what makes you think it won't go through? (OK, someone else
might steal the line while we are waiting...). Of course, after the two
seconds, if the line is busy, they will hear busy, and then be able to
decide the best course of action.... Perhaps retry, etc...

In any case, whether you use a group, or play ringing, or don't, etc...
IMHO, is irrelevant, what all of these dialplans are missing is the
importance of NOT disconnecting an emergency call which is in-progress.

Of course, that is just my 0.02c worth...

Regards,
Adam