This optical counter was found in a 1964 Electronics Design. It makes use of an uncommon optocoupler today, using emission lamp and a phototransistor.
Based on an LS3404 this circuit was found in the July 1990 issue of Radio Electronics magazine. |...
This circuit uses as a sensor a thermocouple to detect air flow. We found this circuit in a 1980s...
This RF signal meter has a switch position that allows calibration and comparison of low intensity...