Without multiplexers you would have to have 4

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Unformatted text preview: can be combined into one 2-Mbps channel. The narrow-band ISDN, however, cannot support the requirements of several types of data services, especially those needed for multimedia applications. For example, the bandwidth required for full-definition digital video is in the 100 Mbps range. To handle this sort of traffic, as well as bursts of data traffic from computers, broad-band ISDN (often referred to as BISDN) was introduced. B-ISDN is based on optical fibers and asynchronous timedivision multiplexing. The advantage of asynchronous time-division multiplexing over conventional time-division multiplexing is that it allows the total bandwidth available to be divided between contending activities in a much more flexible way. ISDN has become so popular that a term to describe the standard analog service has been coined: Plain Old Telephone Service (POTS). 4. Value Added Network (VAN). Some companies specialize in providing value added data transmission service. The value added over and above the standard services of the common carriers may include electronic mail, data encryption/decryption, access to commercial databases, and code conversion for communication between incompatible computers. These companies normally lease dedicated lines of a common carrier, do value addition to enhance the communication facilities, and then sell that enhanced service. This type of service is popularly known as value-added network (VAN) service. COMMUNICATION PROCESSORS In a data communications network, the task of network designers is to select and coordinate the network components so that the necessary data is moved to the right place, at the right time, with a minimum of errors, and at the lowest possible cost. A number of communication processors (typical micro- or mini- computers) are used by network designers to achieve these goals. The functions of some of the commonly used communication processors are briefly described below. Multiplexers There are many applications in which several terminals are connected to a computer....
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This document was uploaded on 04/07/2014.

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