An auxiliary switch or contact is an electrical switch actuated by a main device (such as a circuit breaker) for signaling or interlocking. It is used to remotely indicate the position of the main circuit breaker contacts, whether open or closed. In addition to indicating position, they can also be used to control relays, indicator lights, and other accessories. Most control systems require auxiliary devices to completely implement the desired control sequence. This is true whether the control system is electric, analog electronic, or digital. More generally, an auxiliary device serves as a secondary or supplemental backup to the primary component.