Found in an Electronics World of 1969, this circuit causes a light bulb to flash along with the audio signal applied to the input. The circuit only works with incandescent lamps. C can be 47 nF to 220 nF.
The load used in this experimental circuit is a small incandescent lamp but it can be replaced by...
Found in an American documentation from 1968, this circuit senses the temperature through an...
Today we have more compact solutions. This is from a Radio Electronics magazine from October 1990....