Page:Incandescent electric lighting- A practical description of the Edison system.djvu/78

 for the melted one, and all is ready for continued operation. When wires are led into houses, a different form of safety-catch is used. That shown in Fig. 21 is intended to be placed in the line immediately within the building before the wires pass through the meter. It is arranged for three wires, and is formed of wood, porcelain, or

. 21.

other suitable insulating material; in it are arranged three sockets, similar to those in which lamps are placed, composed of a screw shell, at the bottom of which is fixed a metal button, the shell and button being separated from each other by the insulating material of the block in which they are mounted. On either side of these sockets is a screw, one of which is connected with the button, and the other with the shell.