[asterisk-dev] chan_phone module - phone_call FXO / FXS mixup?

[Jared Smith]

On Sun, May 19, 2013 at 11:25 AM, Łukasz Zwierko <lzwierko at gmail.com> wrote:

> I'm aware that chan_phone is probably not very widely used, still I'd
> have a question about it. I really do hope Mark Spencer or any module
> co-authors (if there were any) can answer this simple question:
>

I've never used the chan_phone module, nor have I ever had the (mis)fortune
to ever look at that code.  However, I'll point out a couple of things that
might help.

In Asterisk, the confusion between FXO and FXS typically comes from whether
you're talking about the *ports* or the *signaling*.

An FXO port connects to the central office (remember the O in FXO and
Office), but to the central office it acts (or signals) like a station.
Hence an FXO port in Asterisk uses FXS signaling.

An FXS port connections to a station (a telephone), but to the telephone is
acts (or signals) like the central office.  Hence an FXS port uses FXO
signaling.

Last but not least, in most of the configuration files and what code I've
looked at, Asterisk typically deals with the *signaling* side of the
equation.  As I said earlier, I don't know chan_phone at all, but in
chan_dahdi, you'd configure something like "fxsls" signaling for an FXO
port -- where fxsls stands for "FXS Loop Start".

Hopefully that helps get rid of some confusion.

--
Jared Smith
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