Discuss briefly subscriber loop system. Give some technical specification for subscriber lines.

Discuss briefly subscriber loop system. Give some technical specification for subscriber lines.
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1 Answer

Answer :

Subscriber Loop System: Every subscriber in a telephone network is connected generally to the nearest switching office by means of a dedicated pair of wires. Subscriber loop refers to this pair of wires. It is un widely to run physically independent pairs from every subscriber premises to the exchange. It is far easier to lay cables containing a number of pairs of wires for different geographical locations and run individual pairs as required by the subscriber premises.

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Generally four levels of cabling are used as shown in Fig. At the subscriber end, the drop wires are taken to a distribution point. The drop wires are the individual pairs that run into the subscriber premises. At the distribution point, the drop wires are connected to wire pairs in the distribution cables. Many distribution cables from nearby geographical locations are terminated on a feeder point where they are connected to branch feeder cables which, in turn, are connected to the main feeder cable. The main feeder cables carry a larger number of wire pairs, typically 100- 2000, than the distribution cables which carry typically 10-500 pairs. The feeder cables are terminated on a main distribution frame (MDF) at the exchange. The subscriber cable pairs emanating from the exchange are also terminated on the MDF. Subscriber pairs and exchange pairs are interconnected at the MDF by means of jumpers. The MDF thus provides a flexible interconnection mechanism which is very useful in reallocating cable pairs and subscriber numbers. The technical specifications for subscriber lines include: 

1. Diameter of wire

2. D.C. resistance per Km

3. Attenuation per Km 

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