Q. Explain about Subscriber Loop System?

Subscriber Loop System:Each subscriber in a telephone network is connected normally to the nearest switching office by a dedicated pair of wires. Subscriber loop refers to this pair of wires. It's unwidely to run physically independent pairs from every subscriber premises tothe exchange. It is far easier to lay cables comprising a number of pairs of wires for different geographical locations and run individual pairs as required by subscriber premises.

Normally four levels of cabling are used as displayed in figure. At the subscriber end, drop wires are taken to a distribution point. Drop wires are individual pairs which run into the subscriber premises. At distribution point, 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 that, in turn, are connected to main feeder cable. Main feeder cables carry a larger numberof wire pairs, typically 100-2000, than distribution cables that carry typically 10-500 pairs. Feeder cables are terminated on a main distribution frame (MDF) at exchange. Subscriber cable pairs emanating from exchange are also terminated on MDF.