[Asterisk-Users] 911/Emergency calls + Caller ID

[John Todd]

>  >  > Bumping calls to clear a path for 911 is possible within Asterisk
>>  already - see the "SoftHangup" application.
>>  That sounds good, but what can trigger the SoftHangup app to drop other
>>  calls automatically when 911 is dialed?
>
>A short AGI script, perhaps?

It probably would not even require a short AGI.  Define a group of 
Zap lines as your "emergency lines".  Increment a counter every time 
a line in that group is used for an outbound/inbound call, and 
decrement when the line is released (hung up.)  If a 911 call is 
placed, and counter=(max lines in group) then run the SoftHangup and 
hangup the last three or four lines in the group before placing the 
911 call.  It is hopefully the case that your system sees 911 calls 
infrequently enough that a few dropped calls will not be overly 
burdensome.  A sub-counter needs to be kept in order to prevent an 
existing 911 call from being SoftHangup'ed.  It is the case that 911 
calls come in clusters from office environments, where two or three 
people may call about the same issue at the same time, and it would 
be bad form to hang up 911 caller #1 in order to clear the line for 
911 caller #2.  You simply have to judge how many lines are 
appropriate

For simplicity's sake, you may just decide that you should hang up 
Zap/1-21, Zap/1-22, Zap/1-23 anytime you see a 911 call being placed. 
You risk hanging up on your other 911 callers... but everything is 
always a tradeoff.

JT