This symmetric 30 mA x 15 V power supply was found in the Ferranti transistor manual from 1974. Transistors are common types at the time.
Indicated for applications with a PC, this circuit was found in an English documentation from...
The figure shows an excellent benchtop isolation transformer system. This circuit was suggested by...
This circuit of a 1964 Electronic Design uses a photodiode from the time. Modern equivalent can be used....