Don’t tell the co-op board, but I now use this RF fun relay kit to get into my apartment building wirelessly and keylessly, by hacking into its intercom system, which lets you buzz people into the front door.
The kit consist a small printed circuit board and a key fob remote. After enclosing the PCB in a small project box, I simply wired one of its two relays to my intercom’s two Door terminals.
After powering the board up and performing the learning procedure for the remote, the system was ready to go.
My apartment is on the second floor directly above the entry, so the 250-foot range on the transmitter fob is not an issue.
And there you go: a keyless entry. I just buzz myself in. And it’s a rolling code transmitter, so no, not just anyone with a remote can activate the relay.