The output transistors can be BC548 and BC558. The circuit is from a 1975 documentation showing a frequency response from 90 Hz to 12.5 kHz.
This is a conventional circuit with triac but no diac which would be nice in place of R2. In the...
This protection circuit was obtained in a 1969 Electronic Design. The SCR can be the current...
This is a typical source of the time (1989) using the well-known regulator integrated circuit 723....