The present invention provides a thermal transfer sheet, a thermal transfer method and a thermal transfer system using said thermal transfer sheet. The signal processing module is further arranged to enable a piconet to be established where the piconet comprises the network element and the plurality of wireless communication units. At least one region uncoated by said fluorescent material is provided at said interior surface of the glass bulb in manner which creates the appearance of a repeating pattern such that visible light is emitted by said fluorescent material and no visible light is emitted by said at least one region uncoated.