Abstract: An alarm system for reporting the status of a plurality of remote alarm points to a central monitoring station. An alarm status transmitter is located in the vicinity of the alarm points, and includes a selection matrix having sensing inputs coupled to the alarm points for receiving status signals. The transmitter further includes a clock for causing the sequential scanning of the inputs, and adapted to produce a pulse duration modulated (PDM) output signal in response to the scanned status signals. The monitoring station includes means for receiving and demodulating the PDM signal, and a status display for continually displaying the condition of each of the alarm points. The transmitter and receiver are each provided with simplified interfacing means, allowing the system to be applied using various transmission techniques.