Patent ID: 6424257
Filing Date: 2002-07-23
Classification: G08B

Abstract:
A dual mode fire detector usable in first and second different types of alarm systems, the first type of system having a control unit coupled by a cable to a plurality of detectors wherein the detectors, on detecting a fire condition, exhibit a latched alarm indicating condition on the cable, producing a predetermined current flow on the cable, wherein the current flow is detectable by the control unit as an indication of an alarm condition and wherein the control unit interrupts the alarm indicating current flow thereby resetting all of the detectors substantially simultaneously, and, wherein the second type of system has a different control element coupled to a second cable and alarm indicating fire detectors are coupled to the second cable, wherein the fire detectors each produce a current flow in the second cable in response to a fire and wherein the different control element includes circuitry for sending at least one status requesting message to the detectors via the second cable wherein the detectors exhibiting the requested status respond to the different control element's status requesting message by each producing the same current flow on the second cable as the respective detector would produce thereon to indicate a fire, the dual mode detector comprising:a fire sensor; control circuits, coupled to the sensor and couplable to a communication cable, wherein the control circuits receive fire indicating signals from the sensor and status requesting signals from the cable, wherein the control circuits produce a current flow on the cable to indicate a fire condition and the same current flow is produced on the cable, in response to a received status request, to indicate the existence of the requested status, and where in the absence of status requesting signals, only a fire, sensed by the fire sensor produces the current flow.