This circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply voltage and has a 10 Vpp output. The transistors are of the time, but admit equivalents.
The transistors are 2N918, 2N3464 and other RF equivalents of the time for Q1. For Q2, 2N3399, 2N2894...
This circuit, which can be used as a shield, was found in a 90s Electronic Design. The circuit...
This interesting intercom circuit was obtained from an Argentine publication from the 1970s....