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.
We found this preamplifier for recording heads in a 1980s documentation. The circuit can be used...
An advanced motor control software plug-in for Microchip’s MPLAB® X Integrated Development...
This circuit is from Delco Radio found in a 1968’s documentation. The transistors are of the time...