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 appears on this site from different sources. This is from documentation from the...
The circuit shown in the figure consists of a low voltage drop (LDO) regulator for 200 mA using the...
The operating principle of the VCO shown in the figure is the same as the CIR4598 circuit. The...