Abstract: An improved environmental alarm system has centralized control of local sensor display capabilities displays, on the sensor itself, a variety of sensor data including sensor address, and detected levels of one or more environmental conditions. Alphanumeric characters are displayed at individual sensors in response to commands from a master microprocessor directing local sensor display content and timing. A local microcontroller within each sensor interprets the detected signal and prepares a resulting data signal that is available for downloading into the alphanumeric display in compliance with a coded message from the master microprocessor.

Abstract: A magnetically actuated switch system (10) has reduced sensitivity to false alarms and reduced power consumption and resistance to physical and magnetic tampering. The system includes a signal processing circuit controlled by a microprocessor (16) that selectively enables magnetic sensors (12, 38), and compares the corresponding sensor outputs (76) to automatically calibrated level and predetermined timing characteristics.

Abstract: In a central station alarm system the alarm sensors associated with a particular subscriber's premises are monitored by a local control unit associated with those premises and controllable by the subscriber. The local control unit automatically reminds the subscriber when he is supposed to close the premises and turn on the system. The local control unit allows the subscriber to change his expected closing time. The local control unit may also perform various other functions such as automatically cutting off power to low priority alarm sensors during a prolonged power failure, automatically cancelling any audible alarm indication silence commands when there are no alarms to silence, and automatically forming a bridge connection between the remote ends of two communication circuits when there is a break in either circuit.