Found in a Popular Electronics from the 90s, this circuit can act as a transmitter for an audio link. The output transistor admits a higher power equivalent, depending on the LED.
Found in American documentation from the 1970s, this circuit is intended for amplifying analog TV...
Photoelectric cells can be used as sensitive light sensors. However, the low voltage they generate...
This circuit was found in a 90s American documentation. The circuit uses still common components...