This circuit is from American documentation from the 70s. This configuration appears in this section obtained from other sources. The signal is sinusoidal determined in amplitude by D1 and D2.
This circuit controls a relay causing it to open and close its contacts at a speed that depends on the...
This circuit is from an Electronics World of 1968. The transistors are of the time and the power...
This circuit is from a Motorola manual from the 70s. The circuit can be implemented with more...