The transistors of this circuit found in a 1965 magazine can be the BC558 and the sensitive 12 V x 50 mA relay. The other components are common.
This mono circuit for 10 LEDs was found in the January 1991 Radio Electronics magazine. It is...
In the figure we have a line receiver circuit (twisted pair) with the possibility of...
This circuit was originally designed for the practice of Morse code, something common in 1966, the year...