16.1 INTRODUCTION

Switches and relays electrically transfer power or functionality from one circuit to another, resulting in the making or breaking of an electrical circuit. Except for the special class of switches called circuit breakers, the actuation of switches is usually manually applied which differentiates them from relays. This chapter outlines the various types, construction, and operation of switches and relays. This chapter also provides general guidance as to the utilization of these devices in electrical circuits. General information about prevalent failure modes is presented for each device type, and an example of specific analysis procedures is presented for aircraft circuit breakers. Because solid-state devices are covered in Chap. 19, this chapter concentrates on presenting failures specific to contact technology.

Some of the military specifications relevant to switches, circuit breakers, and relays are listed in Table 16.1.1