Found in an Electronics World of 1966 this circuit can be made with current power transistors. It causes colored lamps to flash to the rhythm of the audio signal applied to the input.
Suggested by Texas Instruments in 1980s documentation, this circuit uses a component of the era....
The idea of this simple circuit is to use a tape recorder to key a transmitter in code emission....
This relay circuit with a dual channel MOSFET (not very common today) was found in an old American...