This circuit was obtained from an old American documentation, and practically any general-purpose transistor and sensitive relay can be used according to the supply voltage.
This circuit is from a specialized documentation in 1992 FETs. The L1 coil has 0.07 uH with...
The LM1468L can also be used. The circuit is from Motorola's Linear Interface ICs and the...
This low frequency doubler requires a 50 mV signal at the input. The circuit is from an old...