RF or even switching transistors like the 2N2222 can be used in this circuit. The capacitors are ceramic and the frequency is determined by the crystal.
This simple NiCad battery charger was found in an English documentation. Resistors R2 and R3...
This was a very popular instrument in the workshops of the 60s and 70s. It was a "top of the line"...
We found this circuit in a 1981 publication, when it was still possible to find 22.5 V batteries (used...