braid. The metal is woven directly over the cable as the outer covering. The metal used in this braid is
galvanized steel, bronze, copper, or aluminum. Wire-braid armor is mainly for shipboard use.
STEEL TAPE.A second type of metallic armor is steel tape. Steel tape covering (view B of figure
1-17) is wrapped around the cable and then covered with a serving of jute. There are two types of steel
tape armor. The first is called interlocking armor. Interlocking armor is applied by wrapping the tape
around the cable so that each turn is overlapped by the next and is locked in place. The second type is flat-
band armor. Flat-band armor consists of two layers of steel tape. The first layer is wrapped around the
cable but is not overlapped. The second layer is then wrapped around the cable covering the area that was
not covered by the first layer.
WIRE ARMOR.Wire armor is a layer of wound metal wire wrapped around the cable. Wire
armor is usually made of galvanized steel and can be used over a lead sheath (see view C of figure 1-17).
It can be used with the sheath as a buried cable where moisture is a concern, or without the sheath (view
D of figure 1-17) when used in buildings.
What are the two types of metallic protection?
What are the three types of lead-sheathed cables?
What are the three examples of metallic armor cable that were discussed?
Coaxial cable (figure 1-18) is defined as two concentric wires, cylindrical in shape, separated by a
dielectric of some type. One wire is the center conductor and the other is the outer conductor. These
conductors are covered by a protective jacket. The protective jacket is then covered by an outer protective
Figure 1-18.Coaxial cable.
Coaxial cables are used as transmission lines and are constructed to provide protection against
outside signal interference.
In this chapter you learned that conductors are the means for tying the various components of an
electrical or electronic system together. Many factors determine the type of conductor to be used in a
specific application. In order for you to compare the different types and sizes of conductors, we discussed
the following factors:
Unit SizeThe unit size of a conductor is the mil-foot. A mil-foot is a circular conductor 1foot long
with a diameter of 1 mil (0.001 inch, or one-thousandth of an inch).