> So how come my Fritzbox can do this?  It rejects calls on busy, which then
> relies on how the SIP provider handles this.  This could be a busy tone or
> it could be divert to voicemail.  It can also be an NU tone (e.g.
Sipgate)!
>
> I seem to remember there is a "Busy here" message through SIP?

I think there is some confusion here: the original poster wanted to "busy
out" (to use Andrew's term) the POTS line, not the SIP-line.

Christian

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