Incoming Call Wait for DTMF

Hi All.

Asterisk 11.18.0

I’m looking for a way to trigger a URL call, while I’m on a call.

Perfect example would be, when a door phone rings a ringgroup, I’d like to have the PBX listen for a series of DTMF tones, and when it hears a set DTMF series, the PBX will send a POST or GET request to a URL, which will in turn trigger a relay (ex. buzz a door)

I understand there are bells out there that do the job, however since those bells trigger the buzz on the bell itself, it’s not vandal proof therefor causing a security hazard to the company. I also understand that there are vandal-proof bells, but I thought there must be a way to accomplish this with the cheapest bell out there…

Can anyone guide me to some documentation out there, or perhaps help me write this?