Found in American documentation from the 1990s, this circuit can generate signals of up to a few tens of megahertz. The transistor must be suitable for high frequencies.
With the circuit shown, we have an excellent level for the signal obtained from an electret...
We found this circuit in a 1960 Sylvania transistor manual. The relay can be 12 V and C1...
This circuit is from a Popular Electronics from 1992. The circuit employs an equivalent transistor and...