CH. XIII] SWITCHES, FUSES, CIRCUIT BREAKERS 



SIS 



LW 



FIG. 276. SNAP AND KNIFE SWITCHES SHOWING OPEN AND CLOSED CIRCUIT. 



A Snap switch with circuit closed (current on). 



B Knife switch with circuit closed (current on). 



C Snap switch with circuit open (current off). 



D Knife switch with circuit open (current off). 



A W Wires from the switch to the arc lamp. 



Base The insulating support of the knife switch. 



H Handle of the switch blades. 



L W Supply wires for the electric current to the switch. 



There are two main forms of switches: The knife switch like 

 that shown in fig. 276 B, D, and the snap switch, which rotates 

 (fig. 276 A, C). Any switch to be installed should conform in its 

 construction with the National Electric Code and be plainly marked 

 with its capacity -voltage and amperage and the maker's name. 



712. Installation of a switch. The non-combustible, non- 

 conducting base should be fastened to some support, and then the 

 wires of the line cut and scraped and connected firmly in the bind- 

 ing posts or under the binding screws. If the current is over 30 

 amperes the wires should also be soldered to the switch after the 

 screws are well set down. A switch at the supply for the building 



