This optical counter was found in a 1964 Electronics Design. It makes use of an uncommon optocoupler today, using emission lamp and a phototransistor.
This circuit uses a Hall device from that time as a sensor. The circuit is from an English...
Found in Radio Electronics from the 90s, this siren finds many variations on this site. The...
This audio generator that produces both rectangular and sinusoidal signals was found in a...