Cable System Components

Çtico-oom

S-ubscrl be-r Drops

© 2004 Cisco Systems, Inc. All rights reserved. BCRAN v2.1—4-6

The major components of a cable system include:

■ Antenna site: The location of main receiving antennas for broadcast and satellite reception.

■ Headend: Somewhat analogous to a CO of a telephone company. A facility where signals are received, processed, formatted, and combined for transmission on the distribution network.

■ Transportation network: Used where necessary to link a remote antenna site to a headend or a remote headend to the distribution network. Also used to link microwave, fiber, or coaxial supertrunk.

■ Distribution network: In a classic tree-and-branch cable system, trunk and feeder cables constitute the distribution network. The trunk is the backbone. The trunk distributes signals throughout the community that is being served and typically uses 0.750-inch (19 mm) diameter coaxial cable. The feeder branches off the trunk and passes all of the homes in the service area, typically using 0.500-inch (13 mm) diameter coaxial cable.

■ Subscriber drop: Connection between the feeder portion of distribution network and the subscriber terminal (TV set, VCR, and so forth). Includes coaxial (typically 59-series or 6-series coaxial cable), hardware, passive devices, and set-top box.

This topology minimizes the amount of wiring that is required and is a natural topology for broadcasting. The fundamental technical problem encountered by cable TV engineers is that broadcast analog signal strength attenuates (weakens) as it moves through conducting material.

Outside noise, weather, and temperature changes affect signal strength through coaxial cable.

To combat these problems, cable operators use fiber-optic cable in place of coaxial cable trunks.

0 0

Post a comment