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.
This circuit determines the frequency of a signal by beating with a known signal. The circuit was...
With the values of the components indicated, this timer controls intervals from a few seconds to a...
The purpose of this circuit is to automatically turn a water pump on and off. Sensor 1 is the...