The PK543A apartment intercom amplifier by Alpha Communications of Farmingdale, N.Y., is a self-contained audio and access control system designed for use with 3-, 4- and 5-wire apartment speaker stations. The PK543A provides amplification of two-way audio as well as door control. The unit includes the necessary power circuits required to operate a complete apartment intercom system.
The PK543A features volume and tone controls for audio output adjustments at both the main directory and inside apartment stations. Additional functionality includes multiple entrance operation, relay control of door strikes and electromagnetic locks, three selectable door timing modes, a post-office door lock release, both steady and warble call tones, and more.