A relay is an electrically operated switch that consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits must be controlled by one signal. Relays were first used in long-distance telegraph circuits as signal repeaters, and they were used extensively in telephone exchanges and early computers to perform logical operations.
Relays are used for a wide range of applications such as home automation, cars and bikes (automobiles), industrial applications, DIY Projects, test and measurement equipment, and many more. Depending on the number of contacts and number of circuits it switches, relays can be classified. Relays can switch one or more circuits, and each switch in a relay is referred to as a pole. The number of circuits a relay connects is indicated by throws.
Relays are used wherever it is necessary to control a high power or high voltage circuit with a low power circuit, especially when galvanic isolation is desirable. Relays can detect and isolate faults that occur in a circuit. They can be used in the place of other forms of switches, or they can be specifically designed based on factors such as required amperage. Relays are highly versatile components that are just as effective in complex circuits as in simple ones.
In summary, a relay is an electrically operated switch that is used to control a circuit by an independent low-power signal, or where several circuits must be controlled by one signal. Relays are used for a wide range of applications, and they can detect and isolate faults that occur in a circuit.
