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 circuit is from an 80's publication. The operational ones used are of the time, and must be...
This circuit was found the Optoelectronics Sourcebook by Texas Instruments. Any phototransistor...
The circuit shown in the figure is suggested by Micrel, based on the MIC2570 boost voltage...