This buzzer trigger can be used for small alarms. We find it in an 80’s American documentation. The supply can be done with voltages from 3 to 18 V.
Crystals from 100 kHz to 1 MHz can be used in this 1957 Raytheon circuit. 4 can have values...
Assembled with SMD components this circuit can be very small. The range is a few tens of meters. We...
This circuit can provide a voltage of up to 900 V depending on the input voltage. The diodes must...