This simple tone control using two transistors was found in an Electronics Today International of the 90s. Transistors are general purpose NPN types, like the BC549 for greater gain.
In this oscillator a phase shift network formed by C1, C2, C3 and R1, R3, R4 determine the fase...
For inductive loads we have the configuration shown in the figure. Note that the optical coupler...
This circuit was found in the Linear Applications Handbook by National Semiconductor. It uses...