switch

Device used to turn electrical systems on and off, usually by closing or opening a circuit, or to change the route of a particular current. For example, switches are used to turn a light on or off, to select a channel on a television set, or to set the cooking time on an electric oven.

There are many different types of switches. The flick of a switch is called a throw; the part that is moved is called the pole. A single pole single throw (spst) switch has one pole and one point of contact. A single pole double throw (spdt) has one pole with two possible contact points. A double pole double throw (dpdt) has two poles with two points of contact.

Switches are normally open (no) until pressed to make contact. Some switches can be normally closed (nc) until pressed to break a contact. Push switches can be ‘push to make’ (ptm) or ‘push to break’ (ptb). They can also be latched to stay on. Mechanical switches are usually operated by hand but they can be operated using magnets (reed switch), by movement (piezo transducer, tilt switch), or electronically (relay, transistor). Dimmer switches alter the amount of resistance passing through; they are variable resistors that can also switch on and off.

switch

In computing, a network device which allows the interconnection of a number of computers or local area network (LAN) segments. Switches differ from more traditional bus devices in that when a computer on one socket of the switch needs to talk to another a dedicated path is made through the switch between the two sockets. This allows the computers to communicate at the full speed of the switch, rather than having to compete for a share of the bandwidth on the bus.