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Re: [isn-discuss] Testing ISNs with FreePBX

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  • From: John Todd <>
  • To:
  • Subject: Re: [isn-discuss] Testing ISNs with FreePBX
  • Date: Tue, 27 Oct 2009 18:02:58 -0400

On Oct 27, 2009, at 5:44 PM, Rick van Rein wrote:

Hi Pete,

You can dial 0*739 to get my recording and an echo test. Bandwidth is
probably not that great today, but you should at least get some jittery
audio :)

Thanks -- although I got no audio yet, the call did come through now,
and so it proves my code pretty much correct :-)

You did raise something that I yet have to find out -- namely, if the
local part of an ISN can start with 0. The code I sent assumed not.


The preference is that ISNs local portions do not start with 0, since starting with zero makes it EXTREMELY difficult for dialplan authors to determine number prefix dialing.

The suggested prefix for ISN dialing for North American locations is "012" (to compliment the "011" that is familiar for international dialing.) In many other locations, "off-campus" or "international" dialing starts with "00". If your ISN local component starts with "0", dialplans become very hairy for others to try to determine what type of number is being dialed on a phone that is not a SIP client that presents the entire sequence in one long INVITE. (Think of analog phones connected to ancient switches that happen to have a clever SIP box somewhere in the network - every keystroke moves the call forward, and it's not a full dialed string that is typically managed.)

So the recommended ("SHOULD") method would be to not start local number portions with zeros, but it is not prohibited.


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