Electrical Power Systems Technology

338 Electrical Power Systems Technology

shown in Figure 13-10A, while Figure 13-11 presents a pictorial view of the
same circuit. When control of a lighting fixture from more than two points
is desired, two 3-way switches and one or more 4-way switches are used.
For instance, control of one light from five points could be accomplished
by using a combination of two 3-way switches and three 4-way switches.
Figure 13-12 and 13-13 show a circuit for controlling a light from three lo-
cations. The 3-way switches are always connected to the power panel and
to the light fixture, with the 4-way switch between them. The use of 3-way
and 4-way switch combinations makes it possible to achieve control of a
light from any number of points.
Each lighting-control circuit requires an entirely different type of
switching combination to adequately accomplish control of a lighting fix-
ture. These circuits are usually wired into buildings during construction,

Figure 13-8. Schematic diagram for the control of a light from one location

Figure 13-9. Pictorial view of the circuit shown in Figure 13-8