Communications: electrical – Continuously variable indicating – With meter reading
Patent
1996-09-04
1998-06-02
Zimmerman, Brian
Communications: electrical
Continuously variable indicating
With meter reading
380 23, H04Q 100
Patent
active
057607001
ABSTRACT:
The security system involved in the arming and disarming of a car alarm, includes a transmitter and a receiver. Both transmitter and receiver includes oscillators incorporating a highly accurate and stable quartz time base. Each oscillator drives a respective encoder to develop a pseudo random succession of codes. Reset switches are provided for both transmitter and receiver to synchronize the two oscillators and therefore to synchronize the succession of codes. The receiver includes a decoder for decoding the received signals and a comparator for comparing the decoded signal with the signal generated by the encoder. When equality is detected an arm/disarm circuit is triggered. Because the codes of the transmitter and receiver are continually changing, it makes it very difficult for a thief to produce a coded signal which will trigger the arm/disarm circuit.
REFERENCES:
patent: 4596985 (1986-06-01), Bongard
patent: 4630201 (1986-12-01), White
patent: 4672533 (1987-06-01), Noble
patent: 4736419 (1988-04-01), Roe
patent: 4761808 (1988-08-01), Howard
patent: 4791280 (1988-12-01), O'Connell
patent: 4847614 (1989-07-01), Keller
patent: 5159329 (1992-10-01), Lindmayer et al.
patent: 5239294 (1993-08-01), Flanders
Electronics Research and Design UK Ltd.
Zimmerman Brian
LandOfFree
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