초록 ▼

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, subad

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 receiver-decoder 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.

대표청구항 ▼

An FM wireless security system comprising: (a) a plurality of transmitters operating on the same frequency each of said transmitters having means for transmitting a first predetermined number of identically coded messages within a single transmission period; and (b) receiver decoder means for receiv

An FM wireless security system comprising: (a) a plurality of transmitters operating on the same frequency each of said transmitters having means for transmitting a first predetermined number of identically coded messages within a single transmission period; and (b) receiver decoder means for receiving said coded messages from each of said transmitters said means including automatic frequency control means responsive to a first one of said indentically coded messages for locking said receiver-decoder means to the frequency of each of said transmitters, and further including message verification means for providing an indication for having received a valid transmission from each of said transmitters only upon receipt of a second predetermined number of identically coded messages from each of said transmitters within a preset period of time.