Electrical transmission or interconnection systems – Personnel safety or limit control features – Interlock
Patent
1977-09-19
1979-03-06
Miller, Jr., Stanley D.
Electrical transmission or interconnection systems
Personnel safety or limit control features
Interlock
307DIG1, 307254, 361175, H03K 1700
Patent
active
041432878
ABSTRACT:
The circuit includes a signal input circuit having a light emitting diode that is optically coupled to a phototransistor in a signal output circuit comprising a noise suppression circuit and a Schmitt trigger circuit. The noise suppression circuit comprises a switch portion including a transistor switch and a timing portion including a capacitor. The transistor switch is connected in parallel with the capacitor, and in the quiescent condition of the line isolation circuit, the transistor switch is turned on so as to maintain the capacitor in a discharged condition. When the light emitting diode is illuminated by an input signal exceeding a particular threshold, the phototransistor is turned on, causing the transistor switch to turn off. The charging of the capacitor thereupon commences. The Schmitt trigger circuit is connected to the output of the noise suppression circuit, and if the signal is of sufficient amplitude and duration, the charge on the capacitor reaches the level necessary to operate the Schmitt trigger circuit. Otherwise, the capacitor is discharged by the turning on of the transistor switch responsive to the turning off of the phototransistor.
REFERENCES:
patent: 3665224 (1972-04-01), Kelsey
patent: 3801837 (1974-04-01), Pease et al.
Bell Telephone Laboratories Incorporated
Davis B. P.
Miller, Jr. Stanley D.
Newman Harry L.
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