This circuit is powered by a voltage of 4.5 V, being common in radios of the 60's. The circuit is from Mullard's transistors reference manual.
With this circuit, a relay can be activated from an alternating signal with frequency up to a few...
With this circuit the visually impaired can easily locate important places inside the house, such...
In the figure we have the way to use the transistors of an old-paired pair as a trigger circuit. The...