We found this circuit in a French documentation from the 80's. The components used are still common and the circuit can generate signals from 10 Hz to 100 kHz.
This circuit was published in an English magazine from 1977, but it can be easily assembled since...
The maximum current of this circuit is 1 A. The circuit is from Motorola Linear Interface ICs from...
This circuit is a handset receiver that picks up the signal emitted by a coil under the rug or...