The PK-543A Power Pack Intercom Amplifier is a self contained unit not requiring an external amplifier. The PK-543A is designed for use with most 3-wire, 4-wire and 5-wire apartment stations made by LEE DAN, TekTone, and other popular brands. PK-543A provides amplification control and power circuits needed to operate a complete apartment intercom system. Voice volume control and tone volume control are easily adjustable through the screwdriver slot on the front panel. Additional functions include multi-entrance operation with optional PK-502B, AC or DC door operation selectable by terminal connection with selectable delayed action door release set at the dip switch, post office door lock release and a tone signal to call remote stations. A steady or warble tone can be used to identify calling from the main entrance panel and a call button located at the suite entrance. The PK-543A intercom amplifier is an interchangeable replacement for the TekTone PK543A intercom amplifier.