| 单词 | CATV (Community Antenna TeleVision) |
| 释义 | CATV (Community Antenna TeleVision) More commonly known as cable television or cable TV. In a traditional CATV network, the community antenna comprises multiple satellite and microwave antennas located at a headend, which is the point of signal origin.At the headend, multiple analog broadcast TV signals are interleaved by frequency division multiplexing (FDM) and transmitted downstream over an analog coaxial cable trunk system to the community or neighborhood to be served. In a tree and branch architecture, the trunk system branches off into distribution cables to the neighborhoods, where taps and drops serve to connect individual subscribers, as illustrated in Figure C-1. CATV originated in the mountains of Pennsylvania (United States) in the late 1940s, when there were only a few TV stations, all located in major cities.All TV transmission was broadcast over the air and reception was poor in the cities. In remote rural areas and particularly in mountainous areas where line of sight (LOS) was not possible, reception was awful. John and Margaret Walson, owners of the Service Electric Company, a retail appliance store in Mahanoy City, were having a difficult time selling TV sets as reception was so poor in the valley where the town was situated. In order to demonstrate TV sets to their best advantage, Mr. Walson placed an antenna on top of a tall utility pole on a nearby mountaintop and ran antenna wire to the store. In June 1948, he built some amplifiers to bring the signal to customers who had bought his TV sets, thereby creating the first CATV network. Walson also was the first to use microwave to import TV signals from distant stations and the first to use coaxial cable to improve reception. In 1972, Walson also was the first to distribute Home Box Office (HBO), which marked the beginning of pay TV and the explosive growth of the CATV industry. CATV remains largely a North American phenomenon, although CATV is widely available in England and a few other countries. 74570c03.qxd 9/11/07 12:19 PM Page 87 |
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