We do have copper lines to verify which is why I am here asking for help with my VG configs Cass... hehehe.

We have not had any issues with fax lines or modems, just fire alarm dialer modems.

When the modem dials the other end... in this case the master fire alarm server to "check in" so to speak, the handshake takes place and connection is established, however when the data flow starts something is happening and the call is being dropped. We were thinking perhaps DTMF tones on the voice_ports (timing digit, timing inter-digit) or something else...

Did you every figure anything out regarding the VGs working with fire alarms? 

It’s possible your alarms use the Ademco Contact ID protocol - a DTMF based protocol (rather than using modem tones) used to communicate over the PSTN (eg. back to base monitoring). The DTMF tones are very short duration – typically in the range of 40-60msec. On a conventional TDM telephone system, this does not cause any issues as the network passes any tones and does not care about the actual duration of the tones.

On a VoIP system with DTMF relay in place the DSP may detect these tones but discard them because they are considered too short, meaning no DTMF tones will be relayed out of band and the alarm call will fail.

We’ve had success using g.711 and disabling DTMF relay so the tones stay inband, we’ve done this with a VG224 with h.323 dial-peers pointed to another h.323 gateway (29xx router) with a PRI.

Jonathan,

Thanks for your reply. I confirmed with the Technician that the pannels do use "Contact ID". We are moving the line back to the old tmd pbx system temporarly untill we can get a working configuration and any additional equipment we need to support passing the DTMF tones across the network to our LD PRIs. Thanks for your input. I was able to find some documentation on the protocol:

Digital Communication Standard - Ademco ® Contact ID Protocol

I am glad to here that you and other have found workable solution for your enviorments. We will be working with a partner to design a scalable solution as that remote campuse will be adding more buildings in the future.

   Hello, Jonathan.

  I am more of an end user than an IT person.

  Could you help to explain how this would be entered? (I'm sorry, but I am trying to pass this on to IT as they can't seem to figure it out.) They are currently using MGCP, I am told. (I think you can used different Protocals on different Ports, but I don't understand exactly how.)

  I need 2 Lines to work with Alarm Dialers which have short duration DTMF Signals.

  Thanks for any help.

  Robert

Robert,

We end up having to convert our MGCP gateway (a cisco router) to h323 and connecting the alarm lines directly to it.

The issue is that the dtmf tone must be kept inband and in some case could still get croupted across the network.

The is why we converted our gateway which the pstn connects to to h323. Basicly this allowed us to keep a tdm to tdm connection without sending anything over the network.

It doesn't just matter that the port with the alarms is configured for h323, the connection to the pstn would also have to be h323. If not it will still fail.

I am not infavor mixing the protocols for ports on a gateway. I would rather have a seprate gateway for alarms from other devices such analog service (plain old voice), fax and modems.

Very useful post. I am in the same perdicament. I have firealarms of multiple flavors, secure phones and modems. The only thing working is the firewalarms becasue they made the ISR a h232. But I cannot get my modems and secure phones to work because they love mgcp. My 2 ISR's serve as the ISDN T-1 backbone and 3 vg's serve as my analog lines for these systems.