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September 25 2012


Exchanging the private branch - Yate!

Good evening. For years - specifically since 2005 - the eventphone crew has been using the rather versatile software PBX Asterisk. It provides flexible scripting support, SIP trunking, mISDN and many more features desperately needed for our telephony setup. At first we connected the 4400 (proprietary PBX) to Asterisk 1.2 via mISDN1 and Cologne Chip E2 - that was around WTH 2005. For some reason, Asterisk had to be started within a 'while true' loop at the hacker event. I wonder why.
As the years passed, mISDN (Linux kernel ISDN driver) and Asterisk's chan_misdn module were taking turns to being incompatible with each other. One time we happened to observe audio bit calculation errors increasing with each ISDN channel used. With 2 channels the error may not even be heard, but we had 30. Lucky for us there has always been a suitable combination of mISDN, chan_misdn and Asterisk, which worked for us.
Then, a few years later Jolly renamed isdn4linux to LCR (Linux Call Router) with heavy enhancements. And LCR comes with its own Asterisk channel module chan_lcr. At the same time Asterisk's chan_misdn stopped being maintained. So we switched to the slightly more complicated but surprisingly stable setup 4400--LCR--asterisk. Although, during hacker events, the 'while true' was still in place.
This year, LCR added SIP support. And the 29c3 is near. I will only add this much to the rumour mill: PoC-Apps have already been updated.

March 23 2010

Asterisk and the Blink

It's just one of those spring days where your may wonder how to control your friendly BlinkenLights neighbourhood building with Asterisk. Ordinarily the installation comes with a control program called BlinkenLights Chaos Control Center (BLCCC) which can be seen as a jukebox controller handling movies and games. The BLCCC expects incoming ISDN phone calls to be relayed by a UDP based protocol. A suitable Asterisk AGI application can now take over the role of a mediator between ISDN and BLCCC, thus transparently substitute a real ISDN line.

The PoC version of this mediator program is the newest extension to the PoC Telephony Application Suite.
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