Crossbar switch

I want to introduct something about .




A crossbar switch (also known as cross-point switch, crosspoint switch, or matrix switch) is a switch connecting multiple inputs to multiple outputs in a matrix manner. Originally the term was used literally, for a matrix switch controlled by a grid of crossing metal bars, and later was broadened to matrix switches in general. It is one of the principal switch architectures, together with a memory switch and a crossover switch.

Contents

1 General properties

2 Applications

3 Implementations

3.1 Mechanical

3.2 Electromechanical / telephony

3.3 Telephone exchange

3.4 Semiconductor

4 Arbitration

5 See also

6 References

7 External links


//


General properties

A crossbar switch has a characteristic matrix of switches between the inputs and the outputs. If the switch has M inputs and N outputs, then a crossbar has a matrix with M x N cross-points or places where the "bars" cross. A given crossbar is a single layer, non-blocking switch. Collections of crossbars can be used to implement multiple layer and/or blocking switches.

Applications

Crossbar switches are most famously used in information processing applications such as telephony and packet switching, but they are also used in applications such as mechanical sorting machines with inputs. The crossbar "format" is also used in some semiconductor memory devices (see nanotechnology). Here the "bars" are extremely thin metal wires, and the "switches" are fusible links. The fuses are blown or opened using high voltage and read using low voltage. Such devices are called Programmable read-only memory. At the 2008 NSTI Nanotechnology Conference a paper was presented which discussed a nanoscale crossbar implementation of an adding circuit used as an alternative to logic gates for computation.

Implementations

Historically, a crossbar switch consisted of metal bars associated with each input and output, controlling movable contacts at each cross-point. In the later part of the 20th Century these literal crossbar switches declined and the term came to be used figuratively for rectangular array switches in general. Modern "crossbar switches" are usually implemented with semiconductor technology. An important emerging class of optical crossbars are being implemented with MEMS technology.

Mechanical

A type of middle 19th Century telegraph exchange consisted of a grid of vertical and horizontal brass bars with a hole at each intersection. The operator inserted a brass pin to connect one telegraph line to another.

Electromechanical / telephony

A telephony crossbar switch is an electromechanical device for switching telephone calls. The first design of what is now called a crossbar switch was Western Electric's "coordinate selector" of 1915. It was little used in America, but the LM Ericsson company used an improved version for rural exchanges in Sweden. To save money on control systems, this system was organized on the stepping switch or selector principle rather than the link principle. The system design used in AT&T's 1XB crossbar exchanges, which entered revenue service from 1938, was developed by Bell Telephone Labs, based on the rediscovered link principle. Delayed by the Second World War, several millions of urban 1XB lines were installed from the 1950s in the United States. Crossbar switching quickly spread to the rest of the world, replacing most earlier designs like the Strowger and Panel systems in larger installations in the U.S. Graduating from entirely electromechanical control on introduction, they were gradually elaborated to have full electronic control and a variety of calling features including short-code and speed dialling. In the UK the Plessey Company produced a range of crossbar exchanges, but their widespread rollout by the British Post Office began later than in other countries, and then was inhibited by the parallel development of TXE reed relay and electronic exchange systems, so they never achieved a large number of customer connections although they did find some success as tandem switch exchanges.

Crossbar switches use switching matrices made from a two-dimensional array of contacts arranged in an x-y format. These switching matrices are operated by a series of horizontal bars arranged over the contacts. Each such "select" bar can be rocked up or down by electromagnets to provide access to two levels of the matrix. A second set of vertical "hold" bars is set at right angles to the first (hence the name, "crossbar") and also operated by electromagnets. The select bars carry spring-loaded wire fingers that operate the contacts beneath the bars. When the select and then the hold electromagnets operate in sequence to move the bars, they trap one of the fingers to close the contacts beneath the point where two bars cross. This then makes the connection through the switch to connect...(and so on)
To get More information , you can visit some products about
kitchen accessory,
temporary tattoo designs,
.
The products should be show more here!