In this chapter, we have discussed some typical cable- and wire-marking systems, electrical diagrams, and some basic safety precautions. A brief summary of these subjects follows:

Cable- and Wire-Marking Systems - Cables and wires must be identified to provide the technician with a means of tracing them when troubleshooting and repairing electrical and electronic systems. The cable and wire-marking systems discussed in this chapter are typical systems.

The number of systems used throughout the Navy is too numerous to discuss.

For the cable or wire identification for a specific piece of equipment, consult the technical manual for that equipment. One wire identification system you will surely come in contact with is the color coding of wires used on electrical power tools and appliances. Remember, the purpose of the green conductor in a power tool or appliance cable is to prevent electrical shock to the operator in case there is an electrical short to the frame of the appliance or tool.

Electrical Diagrams - Examples of electrical diagrams you will be required to "read" (interpret) and their uses are as follows:

Pictorial Diagram - Shows a picture or sketch of the various components of a system and the wiring between the components. This diagram is used to identify the components of a system.

Isometric Diagram - Shows the outline of a ship, airplane, or piece of equipment. This diagram shows the components and the cable runs between the components. This diagram is used to locate components in a system.

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.

Safety - All individuals are responsible for understanding and complying with safety standards and regulations established to prevent injury to themselves and others and damage to property and equipment.

Having safe working habits and adhering to safety precautions protects YOU and YOUR SHIPMATES. Follow safety precautions to the letter. DO NOT TAKE CHANCES. Carelessness could cost you your life.