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Switch Release Detector Circuit

IP.com Disclosure Number: IPCOM000081674D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Magrisso, IB: AUTHOR

Abstract

An output signal free of noise is generated in response to pressing and releasing a push-button key 10, Fig. 1. Push-button key 10 is normally in contact with terminal 11 and upon being operated it makes contact with terminal 12. As the key leaves terminal 11, there is normally a contact bounce signal as represented in waveform B, Fig. 2. This contact bounce signal is other than spurious system noise which is filtered by resistors R1, R2, R3, R4 and capacitors C1 and C2. Then, as contact is made with terminal 12, a contact bounce signal occurs as seen in waveform A, Fig. 2.

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Switch Release Detector Circuit

An output signal free of noise is generated in response to pressing and releasing a push-button key 10, Fig. 1. Push-button key 10 is normally in contact with terminal 11 and upon being operated it makes contact with terminal 12. As the key leaves terminal 11, there is normally a contact bounce signal as represented in waveform B, Fig. 2. This contact bounce signal is other than spurious system noise which is filtered by resistors R1, R2, R3, R4 and capacitors C1 and C2. Then, as contact is made with terminal 12, a contact bounce signal occurs as seen in waveform A, Fig. 2.

The signal from terminal 12 is applied to OR circuit 13 which together with OR circuit 14 forms latch 15. The output of latch 15 is applied to AND circuit 16, which controls the setting of latch 19 formed by OR circuits 17 and 18. AND circuit 16 cannot set latch 19 until push-button key 10 is released and again makes contact with terminal The output signal from latch 19 resets latch 15; however, latch 19 must be reset from an external source.

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