[sdiy] interlocking switches

[John Speth]

> There is a super-neat solution if you don't need
> more than four interlocking 
> buttons. I'll try to describe it in words...
> 
> 1. Connect the four switches to the four inputs of a
> 4-16 line decoder IC 
> (e.g. 74154, 4514).

That's what I was going to suggest.  Over 20 years ago
I saw this implementation in EDN but it was done with
resistors instead of transistors.  I built it up as an
octave selector and have long since lost the
schematics.  It worked very well and did indeed latch
after momentary contact.  Much cheaper than a
microcontroller but limited to just one function.

I can't remember if I used LS TTL (which was used
heavily in those days) or CMOS (which seemed to have
limited support except from RCA).

(It's the "radio button" device)

JJS


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