CH. XIII] 



SWITCHES, FUSES, CIRCUIT BREAKERS 



517 



advantageous to enclose the switch in a metal box with a slit 

 allowing the handle to project and move so that the switch can be 

 opened and closed. As only the handle is exposed with this arrang- 

 ment the operator is safe when manipulating the switch in the dark 

 (fig. 278). See also 714. 



713. End of the switch to connect with the supply wires. 



Sometimes the supply wires are connected with the hinge end of the 

 switch as in fig. 2. This has the disadvantage that the switch is 

 then energized up to the break at the handle, when the main supply 

 is on. As the switch is liable to get out of order and need screwing 

 up occasionally it is better to insert the lead wires in the opposite or 



FIG. 278. ENCLOSED SWITCH IN A HORIZONTAL POSITION. 



Commencing at the right: 



L W Supply or line wires from the outlet box (fig. 270) to the table switch. 



k Key for locking the metal cover when it is closed. 



H Handle of the knife switch. It projects through the slot (5) in the cover. 

 In the position shown the switch is open. 



sb Switch box. This is a sheet iron box enclosing the switch so that noth- 

 ing can come in contact with the naked metal of the switch. Only the switch 

 handle projects beyond the box. The enclosing box is represented as trans- 

 parent in order to show the switch and its connecting wires within. The bot- 

 tom of the enclosing box is covered with asbestos board and the switch base 

 rests on the asbestos, not on the metal of the box. 



hg Hinge of the metal cover. By turning the cover over to the left the 

 entire switch is exposed. 



A W Wires from the switch to the arc lamp. 



