This 5.1 MHz circuit was found in a 1980s documentation. The frequency is given by the crystal and general purpose transistors can be used.
This circuit was found in a 1967 Electronics World. SCRs are according the controller load,...
We found this configuration in an early 1977 publication. The PNP transistor may be the BC558 and...
This circuit of a Popular Electronics is intended to control a wiper. The circuit consists of a...