Using LM3909 integrated circuits, this circuit was found in an American documentation from the 90's. The frequencies can be changed by changing the capacitors.
This circuit was found in old documentation. The SCR can be any of the 106 family. Note the sensor...
This circuit was found in Ferranti's 1974 transistor manual. The transistors are from the period and...
Short duration pulses can be obtained with the relaxation oscillator that uses common transistors and is...