Figure AII-2.—Isometric wiring diagram of a refrigerator.
interconnections for selected components in a
single-line diagram, as there are in a block diagram.
The single-line diagram is a simplified type of
diagram and should be used primarily to understand, in
broad terms, the function of each of the various
components in the total system.
Schematic Diagram
A schematic diagram (fig. AII-5) uses graphic
symbols to show both the electrical components and the
functional organization of a circuit. You can use the
schematic diagram to trace a circuit and its functions
without regard to the actual physical size, shape, or
location of the component devices or parts. A
schematic diagram is most useful for learning the
overall operation of a system.
A wiring diagram (fig. AII-6) is a detailed diagram
of each circuit installation showing all of the
wiring, connectors, terminal boards, and electrical
or electronic components of the circuit. It also
identifies wire by wire number or color code.
Wiring diagrams are used to troubleshoot and
repair electrical or electronic circuits.
The schematic diagram discussed previously
should be used to determine the location where the
trouble in the circuit could be when a malfunction
occurs. However, the schematic diagram does not show
the terminals, connector points, and so on, in the circuit.
Therefore, you must use the circuit wiring diagram to
determine where to make the voltage or resistance
checks in the circuit.
Terminal Diagram
A terminal diagram is useful when connecting
wires to terminal boards, relays, switches, and other
AII-4
Figure AII-3.—Block diagram.
Wiring Diagram
