This is a 1960s amplifier setup found in a period publication. The circuit uses a special driver transformer that inverts the phases of the signal to excite the output transistors.
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....