The purpose of an isometric diagram is to assist you in locating a component within a system. If you
do not know where to look for a component, the isometric diagram is of considerable value to you. This
type of diagram shows you the outline of a ship, airplane, or piece of equipment. Within the outline are
drawn the various components of a system in their respective locations. The isometric diagram also shows
the interconnecting cable runs between these components.
Figure 3-7 is an isometric diagram of portions of the same automobile starting and lighting systems
discussed in the pictorial diagram (figure 3-6). The battery, starter, and other components can now be
seen, each in its actual location within the automobile.
Figure 3-7.Isometric diagram.
A block diagram is used primarily to present a general description of a system and its functions. This
type of diagram is generally used in conjunction with text material. A block diagram shows the major
components of a system and the interconnections of these components. All components are shown in
block form, and each block is labeled for identification purposes.
The block diagram shown in figure 3-8 is an illustration of an automobile's electrical power, starting,
and ignition systems. It must be emphasized that the following explanation is primarily for the purpose of
assisting you in learning to "read" or interpret a block diagram. The explanation of the functions of the
automobile power, starting, and ignition systems is of secondary importance. By tracing from component
to component in the block diagram and following the explanation, you are given a general description of
the system functions. In addition, you should be able to understand the arrangement of the components in
a block diagram.