Originally Posted by
InSoMnIaC
on the A300 if one switch is stuck in one position due to an internal failure, the action of moving the pitch trim ‘dual lever’ will automatically disengage the pitch trim, requiring pilot action on the overhead panel to reengage it. This automatic protection essentially requires the switch design that we see where both switches are mechanically linked. Because a boeing type, dual rocker design would cause constant pitch trim disengagements
That is not detecting that there is a problem developing; that is detecting that a failure has already occurred. I don't see that this detection requires them to be mechanically linked. Separated toggles would act the same way as they are effectively joined by the thumb of the pilot. There will always be a delay between the operation of independent switches, even if joined together by a single toggle and so there will be a timer to determine how long they can be out of synchronization before deciding there is an error.
If one cares to, look at the problem of switch debounce. A typical switch makes dozens of separate contacts as it is moved into position, opening and closing dozens of times before finally settling down over a period of hundreds of microseconds - ages of time in a digital system. Two switches operated in parallel have no chance of being synchronized over such a period of time.
See
https://www.eejournal.com/article/ul...bounce-part-2/ if curious about debounce. It is a lengthy read, but there are decent diagrams and links to other studies on the topic.