This circuit was obtained from an Electronics World of 1969. General-purpose transistors can be used in this configuration.
This circuit was found in a 1980s documentation. Q1 and Q2 can be BC548 and SCR a TIC106. The...
This traditional symmetric power supply configuration with the 7812 and 7912 regulators was found...
The connection of high-value input resistors causes the circuit to behave like a conventional...