[Asterisk-Users] Sipura 3000 Call waiting on the PSTN line

[Rich Adamson]

Luki wrote:
>> Has anybody been able to get call waiting on the PSTN line?
> As far as I recall, you will only hear a tone in the audio stream when
> a second call comes in. The Sipura does not detect or handle it, but
> if you flash the line on the FXS interface after hearing the tone, the
> Sipura will forward the flash to the FXO interface and hence switch to
> the second call. I am positive this works when the call is picked up
> on the local FXS port but I am not sure if it also works when the call
> is picked up by a remote device.
> 
> This is how I had set it up:
> PSTN -> FXO on Sipura 3K -> Asterisk (remote via DSL) -> FXS on Sipura
> 3K -> Phone
> 
> The call would be re-invited in this case so no RTP traffic goes via
> DSL, only SIP traffic. Switching to second call with flash works in
> this scenario. Additionally I also allowed the call to be received by
> a remote device (RTP via DSL) but I am not sure if you can then use
> Call Waiting (never tried it).

The flash in the above is intercepted and used by the spa3k, and is 
typically used by the sipura for its implementation of special features. 
The flash is not forwarded to the pstn line unless one programs the 
spa3k to operate in a different mode.

Sipura added a configuration option (I think it came out in v3.1.7 code) 
that allows one to program a double-hook-switch-flash that is forwarded 
to the pstn line.

In the OP's config, asterisk is in the middle of the call, therefore 
something would need to be configured in asterisk to handle & generate 
the flash to the pstn interface. But, I've not tried or even researched 
how that might be accomplished.