CH. XIII] 



INSTALLATION OF ARC LAMPS 



503 



one cannot make a wrong connection (fig. 268A). Such an attach- 

 ment would also serve for alternating current, but is unnecessary, 

 as it makes no difference which way the attachment is connected. 



The conductor from the electric supply in the outlet box to the 

 lamp switch, if the distance is small, not over 2 to 3 meters (6 to 10 

 ft.), is most conveniently made of flexible cable of the proper 

 carrying capacity (see the table of carrying capacity of flexible 



FIG. 268. SEPARABLE WALL RECEPTACLES, POLARIZED (A) AND 



NON-POLARIZED (B). 



(Cuts loaned by H. Hubbell, Inc.). 



With direct current, a polarized attachment insures the same polarity with- 

 out attention on the part of the operator; with the non-polarized form there 

 is liability of reversing the polarity unless the connections are specially marked, 

 and care is taken in putting the separable cap in position. Either form can be 

 used with alternating current also. 



electric cables). The two wires or cables are often enclosed in a 

 common sheath. 



698. In connecting the two wires to the attachment cap, the 

 insulation is removed for a short distance (i to 2 cm. y in.), the 

 wires scraped clean, twisted all together, and then turned to a loop 

 to surround the set screw. Great care must be taken to avoid 

 leaving any of the strands free; this would lessen the carrying 

 capacity, but more important still, they might become displaced 

 and make a short circuit (688). 



