Using the integrated circuit 723 we found this power supply in an article in the magazine Radio Electronics from August 1971. The transistor may be a BD136 equipped with a heat sink.
This circuit was found in a Signetics documentation from the 1980s. The integrated is a PLL and...
This two-channel wired intercom was found in the April 1990 issue of Radio Electronics magazine....
The output voltage of the circuit shown in the figure is approximately 7.0 V for a 15 V supply...