The LT1 Lamp tester exites the inert gas within the lamp to test to see if the gas has leaked and therefore able to function and/or enable us to copy a sample. If the lamp glows a light blue then the gas is intact and the lamp should operate. If it glows pink there is a leak and air has entered the tube. It it doesnt glow then the lamp has completely lost vacuum. It is also suitable for testing flourescent lamps used for lighting and is a useful tool for fault finding in factory type environments where stocking and installation of of all such lamps is a common occurance.