This wired intercom circuit was found in an English publication from the 80's. The integrated circuit can be replaced by an equivalent, just like the transistor which is a general-purpose type.
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...