Unsourced material may be challenged and removed. The mechanism of a switch removes or restores the conducting path limit switch types pdf a circuit when it is operated.
It may be operated manually, for example, a light switch or a keyboard button, may be operated by a moving object such as a door, or may be operated by some sensing element for pressure, temperature or flow. A switch will have one or more sets of contacts, which may operate simultaneously, sequentially, or alternately. Switches in high-powered circuits must operate rapidly to prevent destructive arcing, and may include special features to assist in rapidly interrupting a heavy current. Multiple forms of actuators are used for operation by hand or to sense position, level, temperature or flow. Special types are used, for example, for control of machinery, to reverse electric motors, or to sense liquid level.
A common use is control of lighting, where multiple switches may be wired into one circuit to allow convenient control of light fixtures. By analogy with the devices that select one or more possible paths for electric currents, devices that route information in a computer network are also called “switches” – these are more usually more complicated than simple electromechanical toggles or pushbutton devices, and operate without direct human interaction. Each set of contacts can be in one of two states: either “closed” meaning the contacts are touching and electricity can flow between them, or “open”, meaning the contacts are separated and the switch is nonconducting. Automatically operated switches can be used to control the motions of machines, for example, to indicate that a garage door has reached its full open position or that a machine tool is in a position to accept another workpiece. Large switches may be remotely operated by a motor drive mechanism. Some switches are used to isolate electric power from a system, providing a visible point of isolation that can be padlocked if necessary to prevent accidental operation of a machine during maintenance, or to prevent electric shock. An ideal switch would have no voltage drop when closed, and would have no limits on voltage or current rating.
The ideal switch is often used in circuit analysis as it greatly simplifies the system of equations to be solved, but this can lead to a less accurate solution. Theoretical treatment of the effects of non-ideal properties is required in the design of large networks of switches, as for example used in telephone exchanges. A toggle switch in the “on” position. Here the switch is shown in the open position. In electronics, switches are classified according to the arrangement of their contacts. A single-throw switch has one pair of contacts that can either be closed or open. A double-throw switch has a contact that can be connected to either of two other contacts, a triple-throw has a contact which can be connected to one of three other contacts, etc.