For analog lines, this circuit was found in the August 1994 issue of Electronics Now magazine. The transistors are common general-purpose types.
This circuit was found in an American 1980s documentation. Equivalent operational amplifiers can be...
This touch switch is from a 1978 publication. The circuit should not be powered by a...
When a pulse of light reaches the sensor [a CDs cell or LDR] the flip-flop changes its state....