Integrating a dumb doorbell: legrand Selective Call Intercom

[ritchierich]

This older post might give you some ideas. Realize it’s a different system but the OP discusses many things he tried.

Hacking into older wired Intercom system possible?

Since I live in the city mid-rise, I do not have the option to install the new fancy intercoms out there so I have to deal with what the building has (or until they upgrade it). I was wondering if anybody is familiar with the wiring/signals and if there was any way to tap into them to signal Hubitat when someone rings from outside or to open the door. Note: I have access to the relay box and basically there are four wires on both sides: Ground/Power/Ctrl/Audio. On the bottom of the relay box…