Chapter 2 Switches, Protective Devices, and Cables

CHAPTER 2

SWITCHES, PROTECTIVE DEVICES, AND CABLES

LEARNING OBJECTIVES

Upon completion of this chapter, you will be able to do the following:

Describe the characteristics, construction features, applications, and mainte-

nance procedures of the various types of switches, relays, and solenoids.

Identify the characteristics, functions, and maintenance procedures of the

various types of protective devices on IC equipment.

Identify electrical cables by classification, type and size designation, ratings,

and characteristics.

Describe the proper procedures for installing and connecting cables.

Identify the purpose and the installation and maintenance procedures of

radio-frequency coaxial cable.

INTRODUCTION

maximum allowable voltage and current of the circuit

in which the switch is to be used. Since it is placed in

As an Interior Communications (IC) Electrician,

series, all the circuit current will pass through the

you will be working with sophisticated circuitry

switch; because it opens the circuit, the applied

consisting of complex equipment, multiconductor

voltage will appear across the switch in the open

cables and connectors, and a variety of switching and

circuit position. Switch contacts should be opened and

protective devices. This chapter will give you a basic

closed quickly to minimize arcing; therefore, switches

understanding of the hardware that is in general use

normally use a snap action.

with interior communications systems. You will be

able to recognize installations and, with limited

TYPES OF SWITCHES

supervision, you will be able to install this hardware

aboard ship. It should be understood that, due to the

There are many types and classifications of

vast numbers of components used, not every

switches. A common designation is by the number of

component is discussed, but rather the common

poles, throws, and positions. The number of poles

installations. For more detailed information

indicates the number of terminals at which current can

concerning the operation and theory of circuit

enter the switch. The throw of a switch signifies the

switching and protective devices, consult NEETS,

number of circuits each blade or contactor can

Module 3, NAVEDTRA 172-03-00-85.

complete through the switch. The number of positions

indicates the number of places at which the operating

SWITCHES

device (toggle, plunger, and so on) will come to rest.

Another means of classifying switches is the

A basic understanding of switches and their uses

method of actuation; that is, knife, toggle, push button,

is a necessity for the IC Electrician. The Navy uses

or rotary. Further classification includes a description

hundreds of different types of switches.

of switch action, such as on-off, momentary on-off,

A switch is a device used for making, breaking, or

and on-momentary off. Momentary contact switches

changing connections in an electrical circuit. Switches

hold a circuit closed or open only as long as the

are rated in amperes and volts; the rating refers to the

operator deflects the actuating control.

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