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 was obtained in an American documentation translated in the 80's. The circuit can be...
This circuit is from a 1998 Electronics Now and can be easily assembled since it uses a common...
This circuit was suggested by National Semiconductor in its Linear Application Handbook. The...