Wow. I guessed the year correctly. Damn I miss those times. The alarm system was a bit crappy though. 3 digit code, no LED readout on the RKP? Come on. You could have done away with all those signal beeps just to make it more user friendly for the family and you don't have to keep going back and forth to and from the controller and RKP when clearing faults or zone violations. They didn't even have a programmable zone omit from the arming stage. This system is too much of a pain. We had far better in the UK at that time. I suppose this was a DIY kit alarm for budget conscious households being wireless and all. If that's the case it's alright for it's purpose I suppose. Something is better than nothing.
Ah, unfortunately these were actually professionally installed systems. I've seen remnants of a few of these old AT&T security systems, they certainly come across as DIY systems with how sloppy the installs were and how primitive the equipment was.
