This switch or band selector for receivers was found in a Popular Electronics from the 1990s. The circuit uses a PIN diode.
When the light falling on the sensor is cut off, the SCR fires, powering the lamp. Remember that...
When the sensor is wetted by a spray caused by someone falling into a pool or even by a wave...
This traditional TTL anti-clock setting was found in a 1993 American documentation. The circuit...