According to a first aspect of the present disclosed subject matter, a system for wirelessly charging a device, having a built-in coil, via a medium comprising: at least one relay adapted to inductively transfer power for charging the device; and a transmitter configured to inductively transmit to the at least one relay the power for charging the device, wherein the transmitter and the relay are separated by the medium and wherein the relay and the transmitter substantially face each other; wherein the transmitter further comprises a transmitter coil and a transmitter capacitor constituting a transmitter resonance circuit, wherein the relay further comprises a relay coil and a relay capacitor constituting a relay resonance circuit, and wherein a joint resonance frequencies (JRF) of both resonance circuits have a main resonance frequency (MRF); and wherein the transmitter operates at an operational frequency (OPF) selected from a range of OPFs, wherein the range of OPFs is substantially different than the MRF.