This simple radio was found in a Popular Electronics from the 90s. L1 and L2 have 100 turns on a toroidal core and L1 have a socket on the thirtieth turn.
This ultrasonic transmitter was found in a 1974 documentation. The receiver is the CIR11753 or...
This circuit was found in the December 1991 issue of Radio Electronics magazine. The circuit is...
The movement of the LEDs in this circuit mimics the back-and-forth movement of a pendulum, making it...