Abstract: A system, apparatus, and method for maintaining communication integrity in a safety system. A link integrity signal indicative of any short circuits or open circuits in a first communication link is communicated. A control signal having characteristics corresponding to the communication state of the first communication link is generated. A communication link switch is coupled to the first communication link and one or more second communication links; this link switch being controlled in response to the control signal characteristics. If the control signal characteristics indicate that a failure affecting any one or more signals associated with the first communication link has occurred, the connection is switched to one of the second communication links.

Abstract: A system, apparatus, and method for maintaining communication integrity in a safety system. A link integrity signal indicative of any short circuits or open circuits in a first communication link is communicated. A control signal having characteristics corresponding to the communication state of the first communication link is generated. A communication link switch is coupled to the first communication link and one or more second communication links; this link switch being controlled in response to the control signal characteristics. If the control signal characteristics indicate that a failure affecting any one or more signals associated with the first communication link has occurred, the connection is switched to one of the second communication links.

Abstract: A communication line monitor for use in a security or fire detection system of the type including a central alarm station and a communication line. A remote transmitter is coupled to the communication line at the remote end thereof and is assigned one unalterable preassigned address out of 6,561 different addresses. The remote transmitter continuously transmits an eight bit trinary code over the communication line corresponding to its preassigned address. A monitor located at the central alarm station is coupled to the communication line and indicates an alarm condition when the signals received from the remote transmitter fail to correspond to the remote transmitter's preassigned address. The monitor includes a plurality of switches to condition the monitor for identifying the remote transmitter's address. The switches are resettable to any other one of the different addresses.