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 circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply...
This circuit was found in the September 1984 issue of Radio Electronics magazine. The circuit has...
This circuit is regulated by zener and provides a voltage of 9 V. The circuit is from a Radio...