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Block Diagram—Shows the components in block form. Block diagrams are used in conjunction
with text material. They are used to present a general description of a system and its functions.
Single-Line Diagram—Used for essentially the same purpose as the block diagram-to show the
basic functions of a circuit.
Schematic Diagram—Shows, through graphic symbols, the electrical connections and functions of
a specific circuit arrangement. It is used to trace the circuit without regard to the physical size, shape, or
location of the component devices or parts. A schematic diagram shows the overall operation of a system.
It is used during troubleshooting to identify possible circuit malfunction locations.
Wiring Diagram—Is a detailed diagram of each circuit installation showing all wiring, connectors,
terminal boards, and the electrical or electronic components of the circuit. It also identifies the wire-by-
wire numbers or color coding. This diagram must be used in conjunction with a schematic diagram to
troubleshoot a system in order to find the test point for voltage and resistance checks.
Terminal Diagram—Is used in connecting wiring to terminal boards, relays, switches, and other
components of a circuit.
