Found in a 1980s American documentation, this circuit appears with variations elsewhere in this section. The circuit activates a relay according to the supply voltage.
This circuit can be tuned in a 100 kHz band around the frequency of the crystal. The transistor can be...
This high voltage source supplies at its output a voltage that is six times the value of the peak...
This spy transmitter can be plugged directly into a power outlet. The power comes from a regulated...