its end of life a rectifying effect shows up as illustrated by fig4 where voltage magnitude v3 will not be equal to v4 and the dc level will be either positive or negative with a non zero value the principle of the present invention is to detect such non zero dc level if this level exceeds a certain threshold the main alternating power source will be shut down for safe lamp operation now if the lamp rectifying effect is caused by a deteriorated or broken filament filament current detectors 202 or 203 will indicate changes in filament current threshold detection technique can be easily applied for safe and accurate lamp protection in fig5 a first embodiment of the present invention for a fluorescent light system is shown it comprises a primary alternating power source 206 which provides power to a fluorescent lamp through its two terminals the fluorescent lamp has two filaments at its ends and they are powered up by two isolated voltage sources 204 amp 205 these two voltage sources produce voltages with the same magnitude but opposite phases in general these two voltage sources for filament currents are coupled from the primary alternating power source 206 to ensure that they are synchronized the embodiment further comprises of a transformer 504 which has at least three windings namely 501 502 and 503 the filament current signals are picked up by windings 501 and 502 of transformer 504 winding 503 produces a signal in fault conditions which is coupled to a signal conditioning circuit 505 which has an output signal 506 coupled to the primary alternating power source here operation of.