Martin Klier


Asterisk at Usn’s


Asterisk PBX is a very smart telephone system for home, office and enterprise use. In December 2006 I had to decide between purchasing a new ISDN/analogous system for about 2 external ISDN- and 20 internal extension lines or trying something new, even cheaper.

The Pros and Contras of Asterisk for me have been:


  • system has to be reliable (for my parent’s company), but I had no experience with VoIP
  • bad documentation of Asterisk (in 2006 Stefan Wintermeyer said “like sendmail in 1996” 🙂 )
  • nobody could tell me how to use ISDN for outbound lines – everybody used Asterisk for Internet Telephony and their old ISDN phones inside. I intended to do the contrary.


  • it’s something uncommon / new
  • cheap dial switching unit, server alread existed
  • old system straighthroug analogous, new phones needed – why not VoIP hardware?
  • later integration of Internet Telephony very easy

I decided pro Asterisk, and implemented the following:

  1. basic functionality
  2. ISDN inbound/outbound with a Fritz!-Card
  3. four MSNs
  4. four (intersecting) ringing groups
  5. ringing group-dependent outbound caller ID
  6. user-administerable, Asterisk-DB managed call diversion (using call deflect)
  7. inbound limit of calls (Telco’s busy tone if one is already talking)

As soon everyting worked fine, Stefan Wintermeyer released his new book. 🙂 Of course, I bought it – it’s very useful, I’d had less problems with it available just in time… 🙂

Thanks a lot to TheBonsai, too! He often helped, and never asked for place and time!

I will update “Asterisk” section as soon as I find out something new.


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