This circuit was found in a Dutch documentation from 1970. The circuit makes use of semiconductors that have current equivalents and is indicated by a 0-5 mA milliammeter.
This circuit simply triggers an LED when the sensor is activated. The circuit is from a Popular...
This circuit is from a 1972 Motorola publication. The used transistor can still be found, but it...
Found in Popular Electronics from the 90s, this circuit powers a warning lamp when the load is...