the intensity of white light emitted by the leds 22 fourth the dc power is modulated to raise the variations of the frequency of light above the nominal variation of 120 to 100 hz thereby reducing illumination artifacts caused by low frequency light variations including interactions with video screens fifth the dc power may optionally be modulated to provide an alarm function wherein light from the light tube 20 cyclically flashes on and off the one or more current limiting circuits 54 receive the pulse width modulated or switched dc power from the pwm circuit 52 and transmit a regulated amount of power to one or more arrays of leds 22 each current limiting circuit 54 powers a bank of one or more white leds 22 if a bank of leds 22 consists of more than one led the leds are electrically connected in series in an anode to cathode arrangement if brightness or intensity variation between the leds 22 can be tolerated the leds can be electrically connected in parallel the one or more current limiting circuits 54 may include 1 a resistor 2 a current limiting semiconductor circuit or 3 a switching power supply type current limiter fig6 is an electrical schematic of a switching power supply type current limiter 56 the limiter 56 includes an inductor 58 electrically connected in series between the pwm circuit 52 and the array of leds 22 and a power diode 60 electrically connected between ground 62 and a pwm circuit inductor node 64 the diode 60 is designed to begin conduction after the pwm circuit 52 is switched off in this case the value of the inductor.