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Failure Indicator for Multiple Signals

IP.com Disclosure Number: IPCOM000052606D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Anderson, CJ: AUTHOR [+3]

Abstract

System 10 monitors multiple logic signals which must occur repetitively within a given time interval, for visual indication of a failure and isolation of the failing unit.

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Failure Indicator for Multiple Signals

System 10 monitors multiple logic signals which must occur repetitively within a given time interval, for visual indication of a failure and isolation of the failing unit.

CRT display 11 is driven by logic signals for vertical and horizontal synchronization, video data and high intensity, all of which must cycle through both Zero and One levels during every refresh frame of about 20 msec. Logic circuits 12 produce an output signal as soon as every input signal has cycled since the previous output. This output repeatedly triggers single-shot 13, holding it off. If an input signal should become stuck at either a Zero or a One, single- shot 13 will time out and light LED (light-emitting diode) 14, indicating a failure.

For a CRT display 11, logic 12 may implement the following relations among Vertical Sync (VS), Horizontal Sync (HS), Video (V) and High Intensity (H), using three internal latches L1, L2, L3: Set L1 = VS * HS * -V Set L2 = -VS * -HS * V Set L3 = L1 * L2 * H Reset L1 = L3 Reset L2 = L3 Reset L3 = VS * -H Signal L3 provides the output of logic 12, for triggering single-shot 13.

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