Abstract: An annunciator communications system in which any one of a plurality of identical transmitting-receiving units can communicate to the rest through minimum communication links, such as power transmission lines, piping, building structures, or the like. Each unit contains a keyboard encoder controlling the transmitting section of a universal asynchronous receiver/transmitter integrated circuit to generate a modulated 200 Khz output. The receiver section of the integrated circuits in all units on the communications link receives the binary encoded data and passes it to a decoder and multiplexer that controls the input to a six-digit calculator integrated circuit that generates data output signals to a six-digit numeric display.