This circuit was obtained in documentation from the 1980s. The triac and the unijunction support modern equivalents. The trigger transformer is 1: 1 turn ratio.
The circuit in the figure is based on an LM101A; diodes can be replaced with equivalents. The...
This circuit, with magnetic sensor, uses an operational amplifier of the time. The circuit is from...
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...