This circuit is from an old American documentation and its use in motorcycles with 12 V is suggested to power 6V radios. The transistor can be the BD136 and BC548.
Found in a 90s Radio Electronics, this circuit can be used in high voltage experiments, ionizers,...
This VFO circuit generates signals from 2 Hz to 50 Hz. We found it in Popular Electronics from...
This circuit, published in the 1980s, can be applied to operational amplifiers of almost any type....