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 is from an Electronics World of 1964. The circuit can be made with modern...
The Variable Frequency Oscillator (VFO) or Variable Frequency Oscillator shown in the figure can...
This guitar effect circuit was found in a 2002 documentation. The circuit can be powered by a 9 V...