This circuit was found in Motorola's 1968 documentation. The SCRs are then replaceable with current equivalents. The lamp is 24 V according to the power supply.
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...