This circuit was found in a 1965 Electronic Design. What it does is respond only to positive pulses (above zero volts) and can be used in automation systems.
This application is not modern since few computers have parallel ports. But you can use this...
Found in a 1980s manufacturer documentation, this circuit can be used as an optical shield. The...
In the figure we show a circuit in which the output voltage of a 78XX voltage regulator is...