Two ZAP channels and busy signal


I’ve (let’s say) two ZAP “pstn incoming” lines and one SIP phone. Incoming calls from both PSTN lines are routed to one SIP phone. It’s of course working but I’ve one problem:
When user answer call from one PSTN line and other person is trying to call to second pstn it gets “ringing signal” (while user of phone is talking to first person). Call waiting is not a solution because user don’t want to switch between calls.
Both ZAP are analog lines.
And question:

How to simulate busy signal on second line. I can answer second line check phone status and generate busy signal to pstn line but it’s not very elegant way…
The best solution would be: when first line is busy put second line off hook and after ending the call release it but I don’t know how to do it.
I was looking for command like “ZAP off/on hook” selected channel but I can’t find it…

Any ideas?

Best regards


Disable the call waiting function on the SIP phone.


Marco Bruni

[quote=“mbruni”]Disable the call waiting function on the SIP phone.
It won’t work! Because lines are ANALOG the only way to signal “uplink PSTN PBX” busy line i “off hook” these line! And I’m asking how to do it.