Communications: electrical – Digital comparator systems
Patent
1973-11-29
1976-01-06
Boudreau, Leo H.
Communications: electrical
Digital comparator systems
197 98, 235 92CA, 235 92T, 324 60C, 324 60CD, 340365C, B41J 508, G08C 900, G01R 1702
Patent
active
039316106
ABSTRACT:
Each of the inputs of an analog multiplexer are connected to a plurality of capacitive keyswitches and a reference capacitor. At the first multiplexer scan position, the reference capacitor is charged through a charging resistor and when a predetermined voltage is reached a threshold amplifier is caused to respond. The time period required to charge the reference capacitor is stored and compared with the time period required to charge each of the keyswitches. A control signal is generated in response to this comparison providing a signal representative of the capacitive value of the keyswitch in relation to the reference capacitor and thus the operative condition of the keyswitch.
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Marin Robert E.
Simonson Roger K.
Boudreau Leo H.
Landis J. L.
Serp W. K.
Teletype Corporation
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