Dahdi - Dialing out sometimes stumbles upon incoming calls

HI everyone,

Today was our big day, where we switched the company to Asterisk system. There were quite a few issues, but most are now solved.

One issue is when an employee is calling out, and there is an incoming call at the same time, the out calling employee will be connected to the incoming line. It seems to be a problem with asterisk thinking the line is free, but instead there is someone calling in.

I am not sure if that makes sense…
We’ve got 2 x Digium, Inc. Wildcard AEX800 8-port analog card (PCI-Express) (rev 11). We got 10 incoming lines connected to these cards. Incoming and outgoing calls are made through these lines.

We are running Asterisk 1.8.4 with FreePBX 2.9

Any suggestion how to solve this are appreciated.


This is called glare. It is unavoidable on loop start lines. I don’t know if that card supports earth start, although that would also require help from the PTT.

You can minimise it by ensuring that the exchange end hunts across the incoming circuits in the opposite direction to which the PABX hunts across them in outgoing mode.

Thanks David,

At least I know what this occurrence is called.

Is there a way to reverse order in which the outgoing channels are selected?

Right now I have lines connected to channels 5 through 14. Incoming calls come first to channel 5 then 6, 7, 8, 9 etc. How would I make it so the outgoing calls choose channel 14 first, then 13 , etc.

I’ve got these channels are grouped together as g0.

To answer my own question.

In the FreePBX, trunk section:
putting G0 as “DAHDI Identifier” will choose the highest number first.

I guess this should be G1, G2 for g1, and g2 etc.