Optical switch with tamper indicating feature for discouraging t

Details Optical switch with tamper indicating feature for discouraging t Optical switch with tamper indicating feature for discouraging t

1993-04-22

1995-05-09

Allen, Stephone B.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

250221, 315150, 327514, G01J 132

Patent

active

054142547

ABSTRACT:
An optical switch, or detector, is provided with a light source and a light sensitive component. The light source, which can be an infrared light emitting diode, and the light sensitive component, which can be a photodarlington pair, are associated to provide an equilibrium light emission from the light emitting diode which is sufficient to maintain conductance through the light sensitive component which regulates the amount of current flowing through the light emitting diode. This cooperative association between these components results in an equilibrium condition that is disturbed by the existence of an object between these components to obstruct the light beam between the light source and the light sensitive component, or an external light source providing a beam of light received by the light sensitive component. The voltage magnitude at the light source can be used as a signal representing the condition as the light sensitive component. In other words, if an object blocks the light beam between the light source and the photodarlington pair, the voltage at the light source is caused to rise to a predetermined magnitude. If, on the other hand, external light is received by the light sensitive component, the voltage at the light source will drop to a recognizably low magnitude and permit a tampering attempt to be detected.

REFERENCES:
patent: 4520262 (1985-05-01), Denton
patent: 4808809 (1989-02-01), Hayakawa
patent: 4998043 (1991-03-01), Unami et al.
patent: 5298800 (1994-03-01), Dunlop et al.

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