Trigger on outgoing call for busy connection?

[kintrupf]

I have a car alarm which can be toggled on / off by calling a phone number for the build-in SIM card.
The card alarm reacts with one or two busy signals for "alarm is active / inactive" before terminating the connection.
I could not find an option for "call busy" in the Outgoing call action, so I can't automate this reliably.
The option "call ended" is fired even if no connection was made.