Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1977-11-10
1980-09-30
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
343 5PD, 367 94, G08B 1318
Patent
active
042258588
ABSTRACT:
The reflected signal of a microwave or ultrasonic Doppler intrusion detector is split into two different channels, each containing a mixer for hetrodyning the received signal with a reference signal. The reference signal for one mixer is the transmitted signal, while the reference signal for the other mixer is the transmitted signal with a phase shift. Thus the outputs of the mixers are of the same frequency but different phase. A phase comparator produces two mutually exclusive pulse trains as a function of the outputs of the two mixers, one said output representing motion toward the detector and the other representing motion away from the detector. These pulse trains are applied through a bidirectional counter to upper and lower limit sensors. An alarm circuit is activated if either limit is exceeded, thus providing an alarm in response to sufficient motion in either direction.
REFERENCES:
patent: 3796989 (1974-03-01), Ravas et al.
patent: 3838408 (1974-09-01), McMaster
patent: 3845461 (1974-10-01), Foreman
patent: 3846778 (1974-11-01), Galvin et al.
patent: 3987427 (1976-10-01), Clift
patent: 4012730 (1977-03-01), Nicholls
Cole Martin T.
Strahan Graeme R.
I.E.I. Proprietary Limited
Swann III Glen R.
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