Alarm system on TA900 series

[bwireless]

Hey everyone! For sometime now I have been trying to find a way to get an alarm line (secondary fire or security) to work on an FXS ATA of some kind. I have tried Grandstreams, Vegas, Ciscos, and Yeastars to no avail. Recently, I saw someone doing this successfully with a TA9X device and they said they had no issues with it. I went ahead and purchased one for my own testing, but still can't seem to make it work. I have got to be missing something that these alarm systems expect. I have set these up for G.711 ulaw and inband DTMF. I have tried different impedences as well as switching to ground start from loop start, but nothing seems to work. 

If anyone can lend me some advise on how to make this work, or what the alarms want that VoIP can't seem to provide, that would be awesome and highly appreciated!

[jkesting]

Have you tried lowering the baud rate of the interface down to 9600?  I've found that many alarm panels/fax lines struggle with VoIP, but lowering that baud rate has helped me in some cases.  Also enabling modem-passthrough on the voice user account as well as helped.

[stevemiller]

I'd try the following.

If the alarm is transmitting status via modem, lower the baud rate to 9600
If the alarm is transmitting status via DTMF, see if the alarm system can provide 'long' digit duration.
If the issue is with the alarm not detecting adequate loop current, set the FXS port to 'high' battery-mode.
Additionally, take a circuit-loss test from a known working line and compare that to the same test from the TA-9XX and make any Tx/Rx gain adjustments necessary.

I've seen a lot of issues with modem/fax devices and there doesn't seem to be any one 'silver-bullet' for them all. In my experience, the solution was customized almost per site, and sometimes we just couldn't make it work and had to swap back to analog TDM service for those devices.

Ulitmately, fax/modem devices hate VoIP.