These optical relays, which can act as a shield, were found in an American documentation from the 1980s. The circuit has a LDR sensor. It can be adapted for other types of sensors.
This circuit is from a 1968 Electronic Design. The circuit uses transistors of the time that can...
Found in an 1989 R-E Experimenters Handbook, this circuit produces several sound effects that can...
This circuit was obtained from Radio Electronics from the 90s. The infrared sensor is of an...