We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio amplifiers can be used. Transistors are commonly used.
This circuit is from the old RCA transistors manual of 1964. The transistor can be the BC558 and...
Found in a 90s PE Hobbyst Handbook, this circuit mimics the sound of a space gun. The components...
Found on an 80's Radio Electronics, this circuit is designed to pass the 300 to 34,000 Hz voice...