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A Periodic (P)review Of Leaping Forward

By: Johan

Friday, July 14

Tricky Trixbox - Free PBX

Long time no blog! I know... Moving house, business and subsequently ISP = no time for blogging!

So I'm back with a lame post which is basically a 'Note to Self'.

I've bought a Compaq 1.3 Ghz old banger to install Asterisk on, the free PBX. The full newbie program nowadays is called Trixbox. See trixbox.org for more info. They 'advertise' a 1 hour setup so I was rather disappointed it wasn't working at 1.30am after the 3d iso download, the 3d cd-r was burnt and the 4th installation. So I decided to brush up on my Telephony technology knowledge by means of this blog post. Just to define some jargon really.


Stands for Private Branch Exchange. It's basically a device that switches telephone lines using various protocols. The system consists of incoming and outgoing 'trunks', a switchboard and extensions, the end-users. Traditionally they cost thousands of pounds but then a 17 year old wrote a free program called Asterisk which does the same and more. Trixbox is Asterisk + CentOS Linux + FreePBX (GUI) in one and makes up a great, free software PBX that runs on basic hardware from roughly 600Mhz up (PIII, Athlon, Duron & Celeron).


Stands for Foreign Exchange Office. Basically the device that connects the telephony infrastructure with us humans. A simple telephone is an FXO. As far as PBXes are concerned, the FXO is the PCI card that goes into the box, in where one plugs the phone line.


Stands for Foreign Exchange Subscriber. Not entirely sure on this one yet but it seems to be what connects the PBX with a standard phone or other communication device like a Fax. If the FXO is the 'in' then I guess the FXS is the 'out' on a PBX.


This had me guessing for a while but turns out to stand for a "Plain Old Telephone Service". Your bog-standard analogue phone system, nothing fancy, no Voip etc.


Abbreviation for Destination ID. With this ID a call coming into the PBX can be routed directly to an extension bypassing any other interception systems like an IVR. Calls get routed directly to the chosen extension. Like a 301, or portforwarding I guess.


Do we love IVR's or what?! An Interactive Voice Response System is what you get to enjoy when you ring your bank, ISP, insurer etc. "Press 1 for sales, 2 for that..." and then they cut you off :) And I'll be having one of my own at home, just to trick the telemarketers and 'independent' researchers. Asterisk allows a whole maze of a menu, you can upload your own recordings, forward to extensions, start custom programs and more.


Session Initiation Protocol. The preferred protocol for handling sessions during textual communications like Voip, IM etc.


This is the PCI FXO card that goes inside my Trixbox. It has a Motorola chip, is Asterisk compatible and using the Zaptel driver.


The driver that lets Linux talk with the FXO.


Similar to POTS, PSTN stands for Public Switched Telephone Network - that old analogue system Graham Bell was involved with decennia back.

Line Impedance

Analogue phone lines in different parts of the world have different levels of line impedance. Meaning, one FXO with a particular chip might work well in Australia but could be crap (echo etc.) in the United Kingdom.


Pretty self-explanatory, a softphone is a software based phone. A program that emulates a regular phone. Press buttons on the screen to make it dial.


Caller ID. The telephone number of the person ringing. Could be withheld.


An Open Source SID Client by Mozilla.


Stand for Host Media Processing. A HMP Server is typically a server handling telephony, voice, fax etc. services.

So... Now I should know how to get this working...