This QST circuit generates 4 frequency signals according to the crystals used. Transistors admit equivalents although the indicated types can still be found with some ease.
The shock is 2.5mH for frequencies between 3 and 30MHz. C is 1nF, R is 47k and the transistor can...
This circuit allows you to modify the resolution of a measurement bridge. It was found in the...
This circuit with optical couplers was found in General Electric documentation from the 80's. The...