Hello when the switch is off the neon light is in series with the main lamp and like any closed circuit circulates a current that is too small to keep the main lamp off, but if it is enough to keep the neon on. What happens to the flashes? Those lamps that have electronic circuit that small current that circulates thanks to the neon loads a capacitor that is in the circuit of the lamp and when the load of this capacitor is completed it is abruptly discharged on the lamp producing the flash and when emptying the capacitor the cycle returns to start How to avoid this? ... there are two ways. : 1) removing the neon 2) by placing in parallel with the lamp a flash inhibitor so that the discharge of this capacitor instead of being generated on the lamp is generated on the inhibitor the flash inhibitor is nothing other than a small polyester capacitor between 0.22 to 0.47 uF x 400V would come to be as an alternative path in such a way that part of the discharge current is derived to the inhibitor and the absorber lamp is too small to generate the luminosity (flash) regards