Discuss in detail the subscriber loop systems.

Subscriber Loop System: Every subscriber in a telephone network is linked usually to the nearest switching office by means of wire's dedicated pair. Subscriber loop seems as to this pair of wires. This is unwidely to run physically independent pairs from each subscriber premises to the exchange. This is far easier to lay cables having a number of pairs of wires for various geographical locations and run single pairs as needed by the subscriber premises.

FIG - Cable Hierarchy For Subscriber Loops.

MDF = main distribution frame; MF = main feeder; FP = feeder point; BF = branch feeder; DW = drop wires; DP = distribution point; DC = distribution cable

Usually four levels of cabling are used as demonstrated in figure. At the subscriber ending, the drop wires are obtained to a distribution point. The drop wires are the single pairs which run into the subscriber premises. The drop wires are associated to wire pairs in the distribution cables, at the distribution point. Several distribution cables from nearby geographical locations are terminated on a feeder point where they are linked to branch feeder cables that, in turn, are linked to the main feeder cable. This main feeder cables carry a larger number of wire pairs, classically 100 to 2000, than the distribution cables that carry typically 10-500 pairs. These feeder cables are terminated on a main distribution frame (MDF) at the exchange. The subscriber cable pairs emanating by the exchange are also terminated at the MDF.