Tuesday, June 27, 2006

Asterisk & the Digium TDM400P

At last, the Digium TDM400P has received a Telepermit to allow its use in New Zealand. This means that those who are interested in all things VoIP can now try it out for real with their own PABX! For those who are unawares, Asterisk is the way to go, and if you don't want to hack around getting it installed try the Asterisk@Home distro. To source the hardware I can recommend nicegear, and for New Zealand-based support, check out their sister site the New Zealand Asterisk Users Group. We've got a PBX set up at home now, so I thought it would be useful to share the experience.

If you intend on using Asterisk with a landline, make sure you contact your telephony provider to arrange Disconnect Supervision. Basically, the Digium board relies on this extra signalling to know when an incoming landline caller hangs up the phone. If you don't do this, then you'll find that the Digium board won't release the line when remote callers hang up.
If you are a Telecom customer, you need to ring Telecom Business on 126 and ask for "Clear Forward and Answer Reversal". It is available at no cost to business customers. Note that Telecom Residential customers may not be eligible for this service. However, you can try asking for it. Don't call 123 as they won't know what the hell you're on about, call 126 instead.

When installing the hardware drivers, make sure you use the patched version of the driver, as the current Zaptel driver build is not Telepermit compliant. Check out the bottom of the nicegear home page for more information. Make sure that you use the extra command line switches too. More information is available on ASTUG.

If you don't like the multitude of configuration files, you might want to look at using Asterisk RealTime to pull the configuration out of a MySQL database or similar. If you decide to go down this track, make sure you implement RealTime before you get stuck into configuring Asterisk, as it can be painful to retrofit. Note also that RealTime does not seem to be supported by any of the free front-ends for Asterisk, such as FreePBX, so all the configuration might need to be done manually or by using custom scripts.

While not for the faint hearted, Asterisk offers the coolest functionality and utimately the best value for money. After all, you can't beat free!