Supervised wireless security system
First Claim
1. In a wireless security system the combination comprising:
- (a) a transmitter includingi. encoder means for generating a first series of pulses having predetermined pulse widths and a predetermined pulse amplitude, each pulse having a predetermined energy content determined by its pulse width and pulse amplitude, said first series representing a digital code wherein code information is represented by the width of each pulse;
ii. pulse shaping means responsive to said first series of pulses for attenuating the amplitude of a portion of each of said pulses thereby removing a portion of the energy content of each pulse in said first series of pulses while preserving the coded information inherent in said pulse widths;
iii. oscillator means responsive to the output of said pulse shaping means for generating radio frequency pulses representing instantaneous frequency shifts from a nominal oscillation frequency to an actual oscillation frequency wherein the peak amplitude of said frequency shift is greater than or equal to 0.25% of the nominal oscillation frequency; and
(b) a wide bandwidth receiver for receiving said radio frequency pulses including a radio frequency detector, said detector comprisingi. descriminator means for deriving from said radio frequency pulses a pulse train substantially identical to the output of said pulse shaping means;
ii. pulse restoring means responsive to said pulse train for generating a second pulse train substantially identical to said first series of pulses; and
iii. decoding means responsive to said second pulse trail for deriving said digital code therefrom.
2 Assignments
0 Petitions
Accused Products
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 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.
114 Citations
8 Claims
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1. In a wireless security system the combination comprising:
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(a) a transmitter including i. encoder means for generating a first series of pulses having predetermined pulse widths and a predetermined pulse amplitude, each pulse having a predetermined energy content determined by its pulse width and pulse amplitude, said first series representing a digital code wherein code information is represented by the width of each pulse; ii. pulse shaping means responsive to said first series of pulses for attenuating the amplitude of a portion of each of said pulses thereby removing a portion of the energy content of each pulse in said first series of pulses while preserving the coded information inherent in said pulse widths; iii. oscillator means responsive to the output of said pulse shaping means for generating radio frequency pulses representing instantaneous frequency shifts from a nominal oscillation frequency to an actual oscillation frequency wherein the peak amplitude of said frequency shift is greater than or equal to 0.25% of the nominal oscillation frequency; and (b) a wide bandwidth receiver for receiving said radio frequency pulses including a radio frequency detector, said detector comprising i. descriminator means for deriving from said radio frequency pulses a pulse train substantially identical to the output of said pulse shaping means; ii. pulse restoring means responsive to said pulse train for generating a second pulse train substantially identical to said first series of pulses; and iii. decoding means responsive to said second pulse trail for deriving said digital code therefrom. - View Dependent Claims (2, 3, 4, 5)
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6. An FM wireless security system comprising:
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(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. - View Dependent Claims (7, 8)
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Specification