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Community Member

Simple MGCP gateway question


I should probably know the answer to this but it's never come up before...

I have a customer with an MGCP gateway that holds a number of FXS ports. One of these ports connects to a phone in their elevator. The phone is old and uses pulse signaling. There doesn't seem to be a way to change it to dtmf. With the port configured for MGCP, I can't break dialtone when dialing. If I put a test set on the port and use DTMF signaling, everything works. I know I could switch the port to H.323 but I'd prefer not to.

Since this is a production gateway (that terminates their PRI as well) I don't want to troubleshoot by trial and error. I'm assuming its possible to do this with MGCP. I'm hoping someone can point me in the right direction.



Re: Simple MGCP gateway question

I know this is possible with H323 but I haven't test it with MGCP before. In MGCP mode, the FXS ports do not outpulse digits, so that would not work.

We support inbound detection of pulses, but not on the oubound. For outbound calls, we only support dtmf

Foreign Exchange Station (FXS) voice ports do not generate out-dialing. Multifrequency tone dialing also is not supported for FXS and FXO.

I will test and get back to you.

BTW which GW you are using?


Re: Simple MGCP gateway question

You could run H323 just for sending calls from that one port, while keeping MGCP active for the remaining ports.

Community Member

Re: Simple MGCP gateway question

Actually, I don't think I can (at least not easily). The outgoing trunk (PRI) is mgcp-controlled and I don't think (although I haven't tried) I can send a call from the an fxs port through the PRI via an H.323 dial peer.

If I'm wrong, let me know.

In any case, I determined that pulse signaling isn't supported in MGCP. I'll probably just use an ATA.

Super Bronze

Re: Simple MGCP gateway question


I think you need to route all calls from the FXS port to CallManager - CallManager will then route the call back to the MGCP PRI for you...

CM acts as a gateway between various protocols, e.g. SCCP phone can communicate with MGCP gateway, which can communicate with a SIP phone.... all because CM sits in the middle.


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Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!

Re: Simple MGCP gateway question


I sure did mean that you can use H323 to send call to CM as a voip call and then hairpin back via MGCP through a route pattern.

Hall of Fame Super Red

Re: Simple MGCP gateway question

Hi Kris,

Sorry to step off topic here but I am curious why you can't just change out the actual Elevator phone? Is it physically impossible or something built in? I have had to work on many Elevator phones over the years, and all of the "old" ones were inside a door within the elevator but could still be changed out with something with similar dimensions.

The other question I have is that most Elevator phones are setup to "Hotline" to a pre-determined number like a Security desk or Alarm company, is that not a solution that could be done here? That way the fact that the old phone uses Pulse dial would not come into play.

Sorry for straying!


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