This circuit was obtained in a publication in 1998 but can be assembled with 2N2222 or even BC548 transistors. It converts communications patterns using the PC as a power source.
This circuit is from a Modern Electronics from April 1990. The circuit can be assembled with BC558...
We find this circuit in a Popular Electronics of the 80's. The frequency range depends on C1 and...
This circuit was obtained in an old Argentine publication, using germanium transistors and...