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This is not a question, I solved it. I set up Asterisk trunks between offices, with encryption, some offices do not have fixed IP and login in to the central server. That all went well. Anybody needs it I will help with config files.

In each office we have PAP2Ts attached to the local asterisk server and talking to Sipgate for their local phone service. It worked. Again, anybody needs the configs I'll be happy to post.

The problem was that I got intermittent calls with one way audio (silent calls) and terrible problems with echo - really serious echo. Calls through Sipgate gave no echo, but I think that was down to them doing excellent echo suppression. I went round the houses for months before I found the answer; it was very simple and cured both the one way audio and the echo.

SeniorGeek
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  • Answering your own questions is explicitly allowed, but please do try to use the Q&A format: post a question and then post a separate answer (which you can then later accept). https://serverfault.com/help/self-answer – HBruijn Jun 19 '23 at 14:51

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The problem was the configuration of the PAP2Ts. Login as Admin, get Advanced mode, tab Regional, down the bottom field "FXS Port Impedance". The error was that I had not set this, and it needed to be the UK standard "370+620||310nF" (the last one in the list). I made that change across the board - then no echo, no one way audio. It is now a phone system with excellent call quality for internal calls and Sipgate calls are spot on too.

SeniorGeek
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