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7 Dec 2006 18:12:45 Multiplexer A multiplexer is a communications device that combines or multiplexes many signals for conduction over a single medium. In a simple form, a multiplexer will have two signal inputs - one control input and one control output. One common example of a multiplexer is the input selector on a home music system. Multiplexers are used in the manufacture of digital semiconductors including CPUs and Graphic Controllers and in communications equipment. A telephone network is a big virtual multiplexer made up of many distinctly smaller multiplexers. It is just impossible to have direct link between one telephone and another telephone. Instead, the network multiplexes or 'muxes' individual telephones together on a tiny number of wires as calls are made. A 'demultiplexer' at the receiving end completes the process by segregating the multiplexed signals from a transmission line. Quite often, a multiplexer and a demultiplexer are put together on a single gadget that is capable of managing outgoing and incoming calls. There are many forms of multiplexers. Time-division multiplexers possess two signal inputs - one control input and one control output. But, instead of a control signal, they interchange between all feasible inputs at exact time intervals. By alternating in this manner, several inputs can share one output. This method is usually employed in long distance telephone lines. This enables many individual phone calls to be combined together without impacting the pace or quality of any of the individual calls. Time-division multiplexers are normally manufactured as semiconductor devices or chips. They may also be made as optical devices in fibre optic applications. Code-division multiplexers are more complex than time-division multiplexers. They were developed during World War II for coding purposes using mathematical techniques. Subsequently, they have been found to be useful in cellular networks. The term Code Division Multiple Access (CDMA) refers to these semiconductor gadgets that work by allotting each input a specific complex mathematical code. Each of the inputs employs its code to the signal it receives and all the signals are sent to the output at the same time. Dense Wavelength Division Multiplexing (DWDM) is the method used to augment the bandwidth capacity of fibre optic systems in telecommunication industries and Community Access Television (CATV). Multiplexers allow operators to increase their capacity and help them provide reliable service while improving their profitability. Links: The Two-Input Multiplexer Content Team -- BSNL Portal -- Intelligroup Asia Pvt. Ltd. |
