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Old 13th May 2013, 11:22   #71 (permalink)
Join Date: Nov 1999
Location: UK
Posts: 884

Interesting thread - only just looked at it.

Regarding PB switches not turning on/off with too brief a push: A lot of electronic circuits now incorporate "de-bounce" logic into their switching. A mechanical electric switch can obviously only be on or off, but sometimes as it is operated, the contacts can bounce, causing several on/offs to occur within microseconds of each other. This is not a problem with say a simple light or a fan, but now that many systems are computer interfaced, a rapid sequence of on/offs can totally confuse a system. Therefore, many switches use de-bounce logic which ignore rapid changes and only register longer term changes.

This is not such a problem with toggle switches, but can be with Airbus pushbutton types. My Airbus training reinforced this by telling me to make (relatively) slow , positive selections on the pushbuttons, and wait to see the integral caption light go on before releasing pressure on the switch.

Even so, I have recently had a yellow pump refuse to switch off via the push button until I tried slowly several times - think this was a fault though.
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