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
Fiu. 268. Separable Wall Receptacles, Polarized (/l) 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-polarizcd 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 (1 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).