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.
This circuit is from a 1978 Texas Instruments optoelectronics manual. The trimpot adjusts the LED...
Found in a 1969 EEE, this circuit is based on an operational amplifier of the time and on old type...
This Wien bridge oscillator was found in Radio Electronics from the 90s. The circuit uses the 741...