alextheblue :
mikeebb :
Interesting. Early Radio Shack (Model 1, possibly also early 2 and 3) had Hall-effect keyswitches. They *did* require debounce routines - early ROMs didn't have one or a good one, resulting in keybounce unless an add-on routine was used. Permanently fixed in the ROM replacement that provided upper/lower case, and in the DOS's.
I thought bounce was an issue mostly with mechanical switches and relays (some designs more than others). Where the metal contacts physically strike and "bounce" away from each other briefly, chattering and causing extremely brief intermittent contact until they settle. This can be filtered or multi-sampled out.
I can't see this sort of thing being an issue with a hall effect switch. Are you SURE the keyboards you're talking about weren't mechanical?
At this remove (Model 1 era was late 1970s) it's hard to be absolutely sure. I don't know where to find the manufacturing data if in fact any were kept. But I was told at the time that they were Hall-effect keyswitches, and in more than 10 years I only had to replace one (became mechanically sticky after about a year - yes, keyswitches were individually replaceable, and this was probably infant mortality). I suspect the keybounce in early machines (mostly Level 1, I never really had it in Level 2 BASIC) was related more to poor software than the switches, and once we moved to (TRS-, L-, New-, etc.)DOS there was never a keyboarding issue. Should also note that they were not "clicky" at all. Simple thunk on reaching the end of the (rather long) key travel.