Power switch

Patent 4538074 Issued on August 27, 1985. Estimated Expiration Date:

August 24, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Abstract Claims Description Full Text

Patent References

3621276

Automatic on/off digitally timed electronic switch
Patent #: 4112764
Issued on: 09/12/1978
Inventor: Turner

Control system capable of accommodating a plurality of momentary switching devices
Patent #: 4134027
Issued on: 01/09/1979
Inventor: Scott , et al.

Timer circuit
Patent #: 4267467
Issued on: 05/12/1981
Inventor: Tsukada

Timer circuit Patent #: 4359655
Issued on: 11/16/1982
Inventor: Fukui

Inventor

Fraden, Jacob

Assignee

Healthcheck Corporation

Application

No. 06/525864 filed on 08/24/1983

US Classes:

307/126, Power or energy307/141, With time delay or retardation means307/141.4, Electrically initiated327/392, Delay controlled switch (e.g., fixed, single time of delay control, etc.)327/425, Bilateral transistor361/196Including semiconductor device connected to timing element

Examiners

Primary: Eisenzopf, Reinhard J.
Assistant: Jennings, Derek S.

Attorney, Agent or Firm

Crutcher; William C.

International Classes

H03K 17/28 (20060101)
H03K 17/30 (20060101)

Abstract

An improved power switch circuit for turning on manually and for turning off either manually or automatically a battery operated electronic instrument. The circuit includes one manual momentary contact on/off switch, a bilateral switch or transmission gate, a microprocessor, and a capacitor that charges to a threshold level when the on/off switch is momentarily closed (on) and that discharges when either the on/off switch is momentarily closed again (off) or after a fixed amount of time has elapsed as determined by the microprocessor. The bilateral switch is switched on when the threshold potential is reached thereby preconditioning the on/off switch for turning the instrument off. The on/off switch can now be closed to discharge the capacitor or the microprocessor can discharge the capacitor thereby switching off the bilateral switch and preconditioning the on/off switch for again turning on the power to the electronic instrument.