TIPS calls overlapping

Donb123

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I don't know if this is a trunk problem or not. I had this problem from time to time under Trixbox and now in IncrediblePBX.

I have a moderate volume system with an 8 port FXO card from Digium.. TDM something. An IVR answers the phone and you can direct dial or dial by name or there are submenus. Sometimes when you pick up the phone to make a call you are actually answering an inbound call. Thoughts?

Thanks in advance!
 

geopeterwc

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Sometimes when you pick up the phone to make a call you are actually answering an inbound call. Thoughts?

What you're experiencing is called "Call Collision" or "glare". This occurs (almost) exclusively with analog phone services - the lines configured onto the Digium card are analog. When an internal phone places a call, the trunk line (DID) is not selected until the number to be called has been completely entered into the iPBX. Coincident with the PBX selecting a DID to place the call, a call is incoming on the same trunk line.

This was a common occurrence when PBXs were exclusively analog on the trunk side of the system. The glare condition would occur most often with "loop-start" trunks. In the days of old, the phone company had a partial solution in offering "ground start" trunks - which provided better call supervision - potentially identifying a trunk line to be in use before it was seized for an outgoing call. But, even that wasn't 100% foolproof.

One attempt to minimize the possibility of call collision was to reverse the order for selecting outgoing trunks from the order of incoming calls. For an active (busy) PBX, this approach would seem to reduce the frequency of call collision. You might experiment with the order of selecting the outgoing routes - though you'd not have the option of grouping all of the 8 DIDs on the Digium card into one outgoing call route. Each DID would require its' own outgoing route.

Multi-line hunting attempts to avoid glare by selecting circuits in opposite preference order so the highest numbered line, which is last choice for incoming calls, is first choice for outgoing calls, like so:
Code:
incoming -->1
            2
            3
            4
            5
            6
            7
            8<-- outgoing

More information that describes the situation that I think that you're experiencing is found here: https://en.wikipedia.org/wiki/Call_collision. Likely there's no simple solution to the problem that you describe as long as analog DIDs are in the system.

/Pete./
 

Donb123

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In case anyone missed it- like I did- there's an option in later versions of Freepbx/IncrediblePBX to sort the order of channels on the trunk for an outbound route. That should do it.
 

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