Check is made for the purpose of identification of breaks of an electric chain. After power off of a contour, check it by means of the lamp sampler equipped with the independent power supply. Connect sampler wires to both ends of a chain if the control lamp lights up, the break in a chain is absent. If the lamp does not light up, then it demonstrates existence in a break chain. Similarly check serviceability of the switch, having connected a sampler to its plugs. At transfer of the switch to situation "Vkl" the lamp of a sampler has to light up.