Another blast from the past, from the same era. This was a general-purpose gadget: a 5V power supply, plus bouncelsss switch, plus a variable frequency TTL square wave generator. This was one of my experiments with making my own circuit boards, starting with copper cladded boards, drawing on the circuit paths with an inert ink, then etching the rest away in acid. Oh, and hand drilling tiny holes. Lots of tiny holes.
Look at all those scrounged parts! -m