[54] SUPERVISED WIRELESS SECURITY SYSTEM
[75] Inventor: William E. Abel, Lake Oswego,
Oreg.
[73] Assignee: Sentrol, Inc., Portland, Oreg.
[21] Appl. No.: 580,877
[22] Filed: Feb. 16,1984
Related U.S. Application Data
[63] Continuation-in-part of Ser. No. 429,116, Sep. 30,1982, Pat. No. 4,523,184.
[51] Int. Q." G08B1/08
[52] U.S. a 340/539; 340/531;
340/346; 455/56
[58] Field of Search 340/539, 506, 531, 532,
340/536, 825.06, 345, 346, 500, 533, 534, 825.21, 825.44, 825.49, 825.45; 455/9, 51, 63, 65, 227, 228, 229, 38, 53, 56
[56] References Cited
U.S. PATENT DOCUMENTS
4,095,211 6/1978 Shaughnessy 340/539
4,109239 8/1978 Davis 340/539
4,442,426 4/1984 Heuschmann et al 340/539
4,462,022 7/1984 Stolarczyk 340/539
Primary Examiner—Donnie L. Crosland
Attorney, Agent, or Firm—Chernoff, Vilhauer, McClung
& Stenzel
[57] ABSTRACT
Apparatus and method for communication by use of a single FM radio frequency, from a plurality of transmitters to a central receiver in a security alarm system or similar system. A transmitter's radio frequency signal is modulated in wide frequency swings to transmit digitally encoded address, subaddress, and sensor status information in a very brief format. The receiver automatically tracks the rapidly varying frequency of the transmitted signal. A transmission is provided periodically from each transmitter, but a very low duty cycle is used to avoid interference among the transmitters. Address and subaddress data identify each transmission and a maintenance warning is provided by the receiverdecoder unit to identify any transmitter which fails to report within a predetermined time. Each significant sensor change initiates a transmission from the related transmitter. Low duty cycle and low transmitter power requirements provide long transmitter battery life.
8 Claims, 15 Drawing Figures
