if the resonance frequencies of each led unit in each pcb strip are configured to differ from each other a matrix is effectively created allowing two dimensional control over light intensity the light intensity of an entire pcb strip is effected by the amplitude of the ac for the pcb strip in question the band pass characteristics of the led units in a strip may optionally overlap to suit a particular light output demands for the backlight for instance this may be needed in case a smooth transition from one zone to another is needed fig4 b shows a simplified arrangement for only dimming and scanning here only one control unit is required thus reducing cost a first pcb strip 430 a then comprises led units 432 a 432 b 432 z a second pcb strip 430 b comprises led units 433 a 433 b 433 z while a last pcb strip 430 z of an arbitrary number of pcb strips comprises led units 439 a 439 b 439 z with this arrangement one control unit 431 provides a current for all pcb strips whereby the current cannot be controlled for an individual strip on the other hand by controlling the frequency of the current light intensity can be controlled for different led units within each light strip in one embodiment the resonance frequencies of led units in the same position of each strip are chosen to be the same within a given fault tolerance such as 1 5 or 10 for example 432 a 433 a and 439 a are chosen to have the same resonance frequency 432 b 433.