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 a traditional mixer version with the operational 741 and appears several times on this...
This common circuit using operational amplifiers was found in the 1993 issue of Radio Electronics Special...
This configuration was found in old documentation and is valid for most general purpose NPN...