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US 4,234,874 AGranted
Alarm system and method thereof
AssigneeInventional/Security Development Corp.
InventorWayne P. Saya
Life of this patent
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AssigneeInventional/Security Development Corp.
InventorWayne P. Saya
Estimating the term…
A burglar or fire alarm is presented which cannot be disabled by cutting the power or telephone lines and which virtually cannot be radio jammed. A radio transmitter comprises an automatic switch which repetitiously and cyclically switches the carrier frequency of the transmitter between a plurality of frequencies in seriatim for transmission of an alarm signal to a distant receiver so that if at least one of the frequencies is rendered unusable by burglars by jamming or the like, the other of said frequencies will still be usable. A tape player provided with a pre-recorded message signalling an alarm condition is connected to modulate the carrier frequencies. A speed adjustment means is provided for the tape player for changing the playing time for said message. The speed adjustment permits the tape player to play back the message for transmission at a plurality of rates including an increased rate too fast for human comprehension for communication with a computer.
An alarm system responsive to an alarm condition detector to communicate a message to a distant radio receiver system operable to receive messages on a plurality of frequencies, featuring fail safe features that prevent disabling the system by cutting wires or jamming transmission, comprising in combination, a battery operated power supply permitting operation when power lines are disabled, a radio transmitter operable from said power supply for transmitting an alarm message on a plurality of different radio broadcast frequency channels receivable by said distant receiver system, alarm message repeater means operable from said power supply having a pre-recorded audio message signal reproducible at audio reproduction rates greatly increased over comprehensible audible speeds and thus incomprehensible to humans and to be transmitted rapidly before jamming analysis can be effective, means responsive to an alarm condition connected for activating said alarm message repeater to modulate said transmitter with said signal at said reproduction rates, and means activating said transmitter to broadcast the recorded signal on each of the different frequency channels including means operable from said power supply selecting a cyclic sequence of said plurality of different frequencies at a repetition rate of a few seconds timed so that the transmitter will repeat the message on each of the plurality of frequencies thereby permitting effective radio transmission of the alarm message to the distant receiver in the presence of jamming of any less than all said plurality of different broadcast frequency channels.
The method of transmitting an alarm signal of the radio broadcast type in response to detection of an alarm condition for reception at a receiver system adapted to receive the message on a plurality of frequency bands in a mode to avoid possibility of disabling the alarm by burglars or arsonists, comprising the steps of, repeating at a repetition rate of a few seconds a recorded audio message upon receipt of an alarm condition at a rate too fast for human comprehension, to thereby reduce the time available for analysis of the signal by an intruder for jamming and the comprehensibility of the message being transmitted, and modulating the audio message upon a succession of cyclically presented frequencies receivable by the receiver system and broadcasting those messages so that the received message on any of the frequencies will indicate an alarm condition, thereby preventing disablement of the system by jamming less than all the cyclically presented frequencies.
Dependencies are inferred from the claim text.