Apparatus and circuit for use with capacitive presence...

Details Apparatus and circuit for use with capacitive presence... Apparatus and circuit for use with capacitive presence...

2007-03-20

2007-03-20

Pham, Toan N. (Department: 2612)

Communications: electrical

Condition responsive indicating system

Specific condition

C340S507000, C340S562000, C324S500000

Reexamination Certificate

active

10398048

ABSTRACT:
A capacitance presence sensing apparatus (10) having a fail-safe circuit (13) and modular units (100). The fail-safe circuit (13) includes delivering a low voltage (FIG.5) to a sensor and connecting voltage through a resistor to an oscillator (18). An opener ground in the circuit changes frequency of the oscillator (18) to indicate a problem With the fail-safe circuit (13). The apparatus also contains a number of inductance coils (28) which may be selected to tune the frequency of the system. Circuitry is provided in cards which may be combined together with receiver transmitter cards (106) and to easily facilitate the use of the system for desired applications.

REFERENCES:
patent: 4336461 (1982-06-01), Ida
patent: 4346371 (1982-08-01), Ida
patent: 4429264 (1984-01-01), Richmond
patent: 4573040 (1986-02-01), Maltby et al.
patent: 5034722 (1991-07-01), Premack
patent: 5334970 (1994-08-01), Bailey
patent: 5337039 (1994-08-01), Simon
patent: 5432498 (1995-07-01), Zilbershtein et al.
patent: 5793293 (1998-08-01), Melamud et al.

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