Posting here first even though it's a biiit off topic only because its rather NYC apartment specific, and I'm hoping somebody who works with these systems may come across it. Let me know if there's a better board for it.

I recently moved into a nice prewar apartment with a good old fashioned apartment buzzer which im trying to hook up into an Arduino in order to buzz people (UPS, Laundry, Myself) into the lobby when I'm not in the apartment. The buzzer's board looks as follows

https://imgur.com/T75ibpW

and the "manual" i found online which seems to match (Note the matching ABCDX on the board)

https://imgur.com/3WGkCyg

My only question is which wire is the incoming "entry request" buzz, and which wire is the outgoing "allow inside" buzz. Anybody every work on installing/fixing these systems and know?

Edit: This project does not in any way involve me leaving the door to my building unlocked via my Arduino for more then a few seconds, nor does it involve me simply letting anybody in that buzzes my apartment unless they buzz during the Fedex/Ups delivery window, in which I'd buzz them up the same way even if i was home.