I've been writing about VoIP and reviewing VoIP products since 1996
, but even I need help once in awhile to figure out how to get a certain VoIP feature to work, how to install an IP-PBX, how to configure an advanced phone feature, etc. Well, recently I had to deploy a FreePBX system in a production environment for another company and I hit a few stumbling blocks that required a call to FreePBX's technical support and I have to say they were very responsive, extremely knowledgeable and very helpful.
One of my first stumbling blocks was getting second dialtone on a specific FXO port simply by pressing one of the line keys on a Grandstream GXP2100 phone. The reason is there is a DoorKing security gate system hooked into one of the Sangoma FXO ports that listens for certain DTMF touchtones to open and close the gate.
First, I had to create three groups in chan_dahdi_groups.conf, which is done in the FreePBX UI via this URL:
group=0 -> FXO trunks - channels 5, 6, and 7 (normal inbound/outbound lines)
group=1 -> FXO trunk - channel 8 (special DoorKing port)
group=2 -> FXS lines - channels 1, 2, 3, and 4 (analog devices)
I separated the DoorKing into its own trunk line group so it wouldn't be used for outbound calling. I also had to change the context to "from-analog" for the FXO ports for routing via channel number to work.