We just started experiencing a strange issue on our OS 7200 with PRI where externally originating calls being forwarded to an external cell phone are timing out after a couple of rings. Nothing has been changed on the system (I'm the only one who has access to it) and this used to work just fine. Basically, we have an extension with it's own DID which is programmed to "forward all" to a cell phone (5.15.6). If I dial the extension associated with the DID from another internal extension/set it works as it should and the cell phone rings until the caller hangs up. If I dial the DID from either another extension/set or from any outside POTS or cell phone, the cell phone being forwarded to rings twice (sometimes once and sometimes three times but mostly twice - think it's time related and not ring count) and the call terminates. The approximate timing is as follows:

- dial DID from external line (using a cell phone for testing)
- in 8 seconds the cell number being forwarded to rings (heard on both cell phones)
- in 4 more seconds the call is terminated

In comparison, if I just dial that external cell from an internal extension, it starts ringing in about 5 seconds and rings forever. I've looked at all of the various timers I could find and tried changing a few of them (i.e. No Ring Wait in 2.6.3, External Forward in 2.5.4, Call Forward Unreachable Time in 5.14.2) but nothing helped. I guess it's possible that something has changed on our PRI but I wanted to see if there are any settings I should be looking at or debugging tools I can use to see how the call is being processed. Any suggestions would be appreciated. Thanks.

Check your external forward and no answer forward timers are set the same

Thanks for the reply. Assuming you mean in 2.5.4, they were different - No Answer Forward Delay was 15 and External Forward Delay was 10. I changed them both to 15 and repeated the tests with the same results as before. Calls from an internal extension to the target extension get forwarded to the cell number properly and it rings until the call is answered. Calls to the DID for the target extension still ring once or twice on the cell phone and then drop. Any other suggestions or should I be taking to our carrier to see if they are dropping the call? Once the call is forwarded, is the OS 7200 still involved in the call (i.e. are we using up two PRI lines) or it it completely handed off to the carrier? The carrier mentioned that release line trunking is not configured on our PRI - could this be part of the problem? If so, it's strange as we haven't changed anything our our PRI since it was setup over ten years ago and this call forwarding used to work. Thanks again.

Just curious in 5.14.5 set ISDN Outgoing Connect when Progress to ON and see if that helps.

You the man - that did it! Just before I read your post I was on the phone with a technician from our carrier who was tracing the PRI traffic and he said that they were not seeing the alert message within the 10 second limit they have and so dropped the call - even though the cell being forwarded to rang once or twice before the call terminates. Once I changed the ISDN Outgoing Connect when Progress to ON it now rings the cell phone continually as it always did. The only perplexing thing is why this has been working for 10+ years and just in the past month has started to be a problem. Any ideas why this might be? Is it possible the cell calls are taking longer to setup than they used to for the few carriers we use for cell phones (one in Canada and a couple in the US)? Is there any downside to turning that setting on? Thanks again - you saved my bacon!

It's possible the carrier made a charge recently that caused this.
I've seen Strange things even within the same carrier (eg sip lines can't call isdn lines, or 1 site can't call another via the sip lines)

To tell you the truth, I don't know as well. We had a customer who was forwarding their calls to an answering service at night. They had a full PRI setup. Then one weekend this just stopped working. I came in on a saturday and setup a work around to make it work. When I came in the following week I was still stuck on the situation. I finally called tech support and they said, turn that feature on. Once I did the forwarding was working just fine. So I honestly have no idea why it just randomly stops working.

Yea, my guess is something changed with the carrier(s) (PRI and cellular) and/or our OS 7200 config that introduced just enough delay so that the calls were no longer completed withing the PRI carrier's 10 second timeout. Anyway, the important thing is that it's working now. Thanks again for the great help!