What Is a Switch?

What Is a Switch?

A switch is an electromechanical device that disconnects or connects the conducting path in an electrical circuit, interrupting or diverting electric current between two points. Switches are commonly used in computers and other electronic devices to control operations, such as lights, keyboards, printers, and industrial machinery. They are also used to connect network segments, boost performance, and make efficient use of bandwidth. Switches come in a variety of configurations, including toggle, dolly, rocker, pushbutton, mercury, and relay switches, as well as specialized types such as reversing switches, light dimmer switches, and circuit breakers.

A network switch works at the data link layer, or Layer 2, of the Open Systems Interconnection (OSI) model, and it accepts packets from access points connected to physical ports and sends them only through the port that leads to a destination device. These are standard components of ethernet networks and work in conjunction with routers and other network devices to deliver information across long distances.

Ethernet switches offer wired connections for devices such as desktop computers, wireless access points (APs), printers, and some internet of things (IoT) sensors to communicate over a network. They support high-speed data transmission, full duplex communication, and are designed to connect devices over long distances without loss of bandwidth.

They do this by noting a device's media access control (MAC) address, a code baked into the network-interface card in each device that plugs into the network with an Ethernet cable. As frames are received by a switch, it builds a dynamic table in memory that stores Physical Port and MAC Address pairs, allowing it to efficiently route and forward data packets to the correct destination. The process is called MAC learning.

The MAC addresses are then placed in a database that the switch uses to intelligently filter traffic, directing each frame only to those ports that lead to the destination device. This reduces the amount of unnecessary traffic that flows to other ports, thereby improving the overall network speed and security.

A switch can be fixed-configuration or managed, and the ports on a switch may be wired or optical fiber. The switch's network speeds range from Fast Ethernet (10/100 Mbps) to Gigabit Ethernet (1 Gbps or more).

Switches are available in many configurations, including single-pole, double-throw (SPST), which has two contacts that either touch to complete the circuit or separate to interrupt the circuit. A wetting current, which is the minimum current that must flow through a switch while it is operating, helps to prevent the formation of insulating oxides on its contacts. Metallurgical considerations, such as conductivity, hardness, and corrosion resistance, help determine the optimal material for a switch's contacts.