Hi,
i've been tasked with helping a customer integrate a legacy pbx to some new SIP terminals.
Call flow is as follows:
PSTN --> PBX / ACD -- call delivered to extension 1001 through 1004. These are analog lines.
The FXS on the PBX is wired to matching FXO on the 2921 Router with the ports configured with PLAR OPX to the SIP devices that are registered to a SIP proxy. So if 1001 gets the call it will go out the analog line, connect to the FXO and Plar to, say 1001 that is the IP phone.
This all works.
Issue is when the terminal needs to transfer the call back into the old pbx. They need to grab dial tone from the FXS off of the pbx through the FXO and send the call back. Everything i've tried to do has failed and is sending me back to a TCL script with some call handling to be able to release the call back to the pbx off of that incoming call leg.
Some extremely nice people have shared a similar TCL script with me, and we are finally attacking it, and trying to understand but if someone has some better ideas or a way to pair down the script to make it easy to follow it would be great.
What i have tried is using CME instead of the sip proxy server and have the terminals register directly. no luck. I used CIPC to see if we can emulate what happens - and actually CIPC has a flash softkey and it worked - so we know it's possible. The flash key does not exist on any SIP profiles for CME. I wanted to pcap a successful flash and transfer but it would not work. Transfer off a cisco ip phone registered as a sip client results in a new call going back, hairpinning the call and not flashing and re-using the same line, and therefore freeing it up.
Any help / direction is appreciated. For those that can help I'll share the TCL with you directly as it is not my work, and was given it by the authors when they solved a similar, but not identical problem. They had a few more constraints. So i know it's doable, i just need help and i'm willing to debug, test and learn.
Thanks
Jim
