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21 Nov 2006 18:07:22 Subscriber Line Interface Circuit chip Subscriber Line Interface Circuit (SLIC) is an Integrated Circuit (IC). The SLIC chip provides the interface between the analog loop of the telecommunication network and the telephone companys central office. The essential functions of SLIC are summed up with the acronym BORSCHT - Battery, Overvoltage, Ringing, Signalling, Coding that involves analog-to-digital and digital-to-analog conversions, Hybrid that entails two-to-four-wire conversion and Test. Environments such as company-to-customer premises connections, Remote Terminal (RT), Private Branch Exchange (PBX) and Digital Loop Carrier (DLC) systems make use of the SLIC. Along with SLIC chips, codec (coder-decoder) chips are used to minimise the number of components usually required to interface an SLIC and codec by almost 90 per cent from nearly 10 components to just one. Codec chips are useful in encoding or decoding, compressing or decompressing different types of data, especially when bulk storage is crucial. The SLIC supplies the power and the ringing signals to the telephone connection and carries the voice signals to the codec chip, on which the signals are transformed from analog to digital and vice-versa. The SLIC and the codec are fixed next to each other on an electronics circuit board. The SLIC chip is used by telephone companies in short-range subscriber loops, such as fixed Wireless Local Loop (WLL), intelligent network terminals and VoIP. Minimising power consumption by SLICs results in the extension of the life of the back-up battery in programmes that are remotely powered such as WLL and brings down the battery size which results in the reduction of costs. A conventional telephone exchange is capable of serving a huge number of telephones linked to it along parallel lines of varying lengths. The variation is because of the difference in the distances of the telephones from the exchange. In addition to carrying communication signals, the exchange also provides each line enough power to run the telephones. It differs from phone to phone based on the length of the lines, which leads to differences in the amount of resistive losses on various lines. The difference in power requirements is reconciled through a number of SLICs, each of which supplies enough power through a specific line to make its telephone function. When linear SLICs are used, the excess power provided to each circuit is scattered as heat. SLICs have individual internal switch mode power supply units that bring down power loss. Such SLICs are expensive. SLICs use +5 V and +3.3 V power. The 1.8 V power essential for the functioning of the cores of Digital Signal Processors is transformed on board from 3.3 V. Some of the SLICs function at both 3.3 V and 5 V. AMD, Lucent, STMicroelectronics, Intersil, Legerity, Ericsson, Silver Telecom, Seltech Electronics, Mitel Semiconductor and Intoto are some of the manufacturers of SLICs. SLICs are used widely in network interface devices, SME gateways, DSL and cable modems, home routers and multimedia terminal adapters. Link: Silicon Wireless Local Loop (WLL) Solutions from AMD Content Team -- BSNL Portal -- Intelligroup Asia Pvt. Ltd. |
