US Patent 9070059 Portable object with self switching device

A portable electronic device 1 comprising a battery 14 coupled with an electronic circuit 10-12 through a switching circuit 15 for switching on or off the supply voltage Vcc to the electronic circuit using the battery. The portable device comprises at least one electromagnetic field detection circuit 13 coupled with the switching circuit 15 to start the power supply to the electronic circuit 10-12 if an electromagnetic field is detected.