This bidirectional circuit was found in an American documentation from the 80's. The LEDs are common red, and the resistor is calculated according to the formulas next to the diagram.
I found this circuit in a 1978 publication. The circuit can be assembled with a BD136 transistor to...
This basic TTL watch and minute clock circuit was found in European documentation from the 1970s....
This simple windscreen wiper interval was found in old American documentation. The relay must have...