530 replacing the permanent magnets 20 and 30 used in the fig2 a the electromagnets 520 and 530 are constructed by a ferro magnetic bobbin like frame with coils 521 and 531 wound between top and bottom bobbin plates it is well understood in the electronic field that when dc signal is applied to the coils 521 and 531 magnetic fields will cause upper plate to be a north pole and bottom plate to be a south pole in this operating mode the dc magnets operate just like the permanent magnets as explained in the fig2 a and fig2 b illustration the excitation signal may be a constant dc supply or a rectified ac signal having electromagnets has the added flexibility of creating special effects since they may be driven with a low power low voltage supply and various control circuits for example adjusting the supplied voltage to the dc coil magnets may be used to control the vibrating strength if the power is completely removed from the dc magnets the vibrating action of u201c i u201d core magnetic laminate will essentially stop even if full power is applied to the u201c i u201d core coil there will be no vibration because.