This circuit operates at a voltage of 1.3 V from a single mercury cell. We found in an old documentation and for the components used the frequency is 500 kHz.
e find this circuit in documentation for radio amateurs of 1974. The unijunction transistor can be...
Circuits similar to this can be found in this section. This is from 1967 General Electric...
This circuit can be made usng the TIP32 transistor but must use carbon microphone (not very common these...