This circuit doubles the frequency of an audio signal, thus changing its timbre. The circuit was found in an Elektor from the 90s. The components are common today.
This circuit was found in old documentation. The SCR can be any of the 106 family. Note the sensor...
This common circuit using a multivibrator causes two lamps to alternately flash at a frequency and active...
Found in an Electronic Design and 1970s, this circuit uses transistors of the time. The...