Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1998-04-16
2000-03-28
Hofsass, Jeffery A.
Communications: electrical
Condition responsive indicating system
Specific condition
340657, 34087026, 714814, G08B 2100
Patent
active
060437499
ABSTRACT:
A frequency detection circuit has a transistor switching device between first and second electric potentials, and a gate applied with a clock signal. A resistor and a capacitor are connected in parallel between the output of the transistor switching device and the second potential. The capacitor is charged toward the first potential when the clock signal assumes one level and discharged toward the second potential in accordance with a time constant determined by the resistor and the capacitor when the clock signal changes to the other level. A comparison device connected to the output of the transistor switching device compares an output voltage of the transistor switching device with a predetermined threshold voltage and delivers an AC signal when the clock signal is small causing the output voltage of the transistor switching device to cross the threshold voltage during discharge of the capacitor, but a DC signal when the frequency of the clock signal is large causing the output voltage of the transistor switching device not to cross the threshold voltage.
REFERENCES:
patent: 4667328 (1987-05-01), Imran
patent: 5416443 (1995-05-01), Cranford, Jr. et al.
patent: 5583819 (1996-12-01), Roesner et al.
patent: 5657361 (1997-08-01), Inagaki et al.
Japanese Office Action with translation of information encircled in red ink.
Patent Abstracts of Japan, vol. 16, No. 412 (E-1256), Aug. 31, 1992.
Funahashi Norio
Saito Hirofumi
Hofsass Jeffery A.
NEC Corporation
Trieu Van T.
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