The statiscope is primarily designed to detect the electric field of a high voltage conductor, whether bare orinsulated. The end of the statiscope just has to come near the conductor, it does not actually have to come in contact with the conductor. In fact, it is probably best that it doesn't unless you know just how high the voltage is. When the presence of a high voltage field is detected, the neon tube will glow. The statiscope should be tested both before and after use by using a known energized high voltage circuit. That is done to be sure that the statiscope has not failed and that it will give, and has given, an accurate display. (One handy use for the statiscope is for checking the presence of proper voltage to auto spark plugs)