I do indeed have a board around here someplace that I
have no info on, b=
ut=20
it's got a row of those -- 12? -- and the outputs of them seem to be coup=
I assume 'those' means HE567s
led=20
to a couple of 7400 chips.
Had it been 7 or 8, I'd have guessed they were set to the row and column
tones for a standard teletphone DTMF keypad, and that the logic combined
them to produce a separate output for each key.
With 12, it _might_ be a selective calling decoder from a private radio
system, or soemthing like that.
-tony