Found in a 1965 CQ magazine, this circuit uses period components. The unijunction transistor can be a 2N2646 and the relay has voltage according to the supply.
This amplifier was found in a Japanese publication in 1972. Transistors are uncommon today, and...
The current of this source is 200 mA at the most, and the output depends on the zener that may...
Found in Mallory documentation from 1968 this circuit uses an integrated circuit from that time. The...