This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent components. The transistors may be BC558 and the transformer is obtained from a disused transistor radio.
Suggested by General Electric in 1980s documentation, this circuit makes use of PUTs that are not...
Found in a 1968 US publication, it is a font filter. The transistor is according to the desired...
This simple measuring bridge allows the capacitance m of some pF to microfarads to be measured...