Mains Tester Screwdriver

tester screwdriver
An electrical tester pen , test pen, or voltage detector is a device for quickly checking whether a conductor is live. The device may have the form of a screwdriver.

mains
(main) any very large body of (salt) water
(main) chief(a): most important element; "the chief aim of living"; "the main doors were of solid glass"; "the principal rivers of America"; "the principal example"; "policemen were primary targets"; "the master bedroom"; "a master switch"
A principal cable carrying electricity
A principal pipe carrying water or gas to buildings, or taking sewage from them
The open ocean
(main) a principal pipe in a system that distributes water or gas or electricity or that collects sewage