This circuit shows how to make an adaptation on an AM receiver to receive CW and SSB signals. The circuit is from an 80's documentation. The diode is commonly used.
This source whose voltage depends only on the zener diode used, can supply currents up to about 3 A....
In the fist circuit the alarm triggers on when any sensor is CUT. In the second circuit the alarm...
Here we show an oscillator that uses an LC network. The upper limit depends on the power-supply...