Back to base alarm monitoring using VoIP
The new FTTN NBN is rolling out my area pretty soon. Switching over from my current ADSL2+ connection will mean disconnecting my analogue phone line, so I’ll need some other for my back to base alarm to contact the monitoring station.
I’ve managed to set this up with the Cisco SPA112 ATA and Nodephone.
- I bought the ATA from IJK for $65.
- Grab the SPA112 Firmware V1.4.1 (mirror).
- Internode’s configuration guide.
- My full configuration.
My alarm has a communicator test function which dials the monitoring centre and sends a test signal. The test passes if the alarm can dial a number and send its codes. This doesn’t mean that the monitoring centre actually received the signal though! To check this I used a RJ12 double-adapter so I could listen in on the alarm while it dialled. I would change some settings on the ATA, run a test and listen. Once it ‘sounded right’ I called the monitoring centre myself and asked them if they received the test signal. They did!
The changes that I think were necessary are:
- Use G.711u as the ‘Preferred codec’.
- Set ‘Use Pref Codec Only’ to yes.
- Disable ‘Silence Supp’.
- Disable ‘Echo Canc’.
- Set ‘DTMF Tx Mode’ to normal.
Because of this trial and error approach I did make many other changes, probably most of them were not needed, but maybe some were! You can see my full configuration in case you’d like to compare. Note that my ATA is dedicated to the alarm, I have it configured to not receive incoming calls.