Communications: electrical – Digital comparator systems
Patent
1976-07-30
1978-02-07
Yusko, Donald J.
Communications: electrical
Digital comparator systems
179 84VF, 307233R, 328140, 329107, H03D 300, H03K 116
Patent
active
040729311
ABSTRACT:
At least one component of a transmitted RF alarm signal is repetitively shifted in frequency between at least first and second frequencies chosen from among a plurality of predetermined frequencies with such shifts in frequency occurring at a predetermined switching rate. A remotely located alarm receiver detects the presence of the predetermined first and second frequencies as well as the presence of the predetermined switching rate therebetween before producing a corresponding alarm output only if both of the predetermined frequencies and the predetermined switching rate therebetween are all concurrently present. Special transmitting circuitry including encoding modulator circuitry is provided. Special decoding circuitry for incorporation at the remotely located receiver of such a system is also provided. The exemplary embodiment of such decoding circuitry incorporates a unique frequency detection circuitry which greatly increases the flexibility and reliability of the overall system.
REFERENCES:
patent: 3548322 (1970-12-01), James
patent: 3825842 (1974-07-01), Birchfield
patent: 3986055 (1976-10-01), Barzely
Scientific-Atlanta, Inc.
Yusko Donald J.
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