The integrated circuit and configuration are uncommon. However, the sound quality is good. The circuit is from the 1983 Intersil Databook. The output transistors must be provided with heat sinks.
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....