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 was obtained in Motorola documentation from 1969. The components are from that time. In...
Originally, this circuit is from an English magazine, but I found it in Argentina's Radio Chassis...
This circuit was obtained in a Electronics World of 1968. The transistors can be equivalent as the BC558...