We found this circuit in a 1998 publication. The circuit has controls for both frequency and signal strength. A lamp is used to monitor the signals. The supply is made with a voltage of 12 V.
This circuit was obtained from a Radio Electronics from October 1963. The 4 transistors must be...
This shield circuit is from an American documentation from 1969. The components can be modified...
This circuit for very low frequencies was found in an American documentation from the 90's....