Found in a 1968 US publication, this circuit produces a delayed pulse with the negative transition of the input signal. The circuit can be used as a shield.
This circuit was obtained from an old American documentation, and practically any general-purpose transistor...
This circuit is intended for monitoring an environment. It fires a relay with a sound, but only if...
This circuit is from an old documentation, but perfectly current. In place of the battery, 2 or 4...