This diagram was found in the November 1972 issue of Radio Electronics magazine in an article describing benchtop equipment. The transistors are of the time and the frequencies are given by the coils.
This circuit is from a 1957 Raytheon transistor manual. The diode can be of general-purpose...
The circuit shown in the figure shuts off a load when the voltage drops below the value determined...
This circuit was obtained from an English magazine from 1976. The signal from the circuit should be...