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Understanding the network.pdf - Back to Home

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Table 5.1. The American (DS) and International (I-DS) DSH<br />

DSH Signal<br />

Level<br />

Transmission<br />

Rate<br />

Number of<br />

DS0<br />

Carrier<br />

System<br />

Transmission Medium<br />

Channels<br />

DS0 64Kbps 1 Analog 24/26 AWG Copper Wire<br />

DS1 1.544Mbps 24 T1 24/26 AWG Copper Wire<br />

I-DS1 2.048Mbps 30 E1 24/26 AWG Copper Wire<br />

DS1C 3.152Mbps 48 T1C 24/26 AWG Copper Wire<br />

I-DS2 8.448Mbps 130 E2 24/26 AWG Copper Wire<br />

DS2 6.312Mbps 96 T2 24/26 AWG Copper Wire<br />

I-DS3 34.368Mbp 480 E3 Coaxial/MM<br />

Microwave<br />

Fiber/<br />

DS3 44.736Mbps 672 T3 Coaxial/MM<br />

Microwave<br />

Fiber/<br />

I-DS4 44.736Mbps 672 E4 Coaxial/MM<br />

Microwave<br />

Fiber/<br />

DS4 274.176Mbps 4032 T4 Coaxial/MM<br />

Microwave<br />

Fiber/<br />

I-DS5 565.148Mbps 7680 E5 Coaxial/MM<br />

Microwave<br />

Fiber/<br />

T1/DS1<br />

The T1 is <strong>the</strong> basic transport facility of <strong>the</strong> T-carrier system. Through <strong>the</strong> use of<br />

multiplexers, faster T-carrier transmission rates are achieved <strong>to</strong> meet <strong>the</strong> DS-X<br />

transport requirements. T1 transmission is facilitated with two conditioned AWG<br />

24/26 copper twisted pairs. A T1 circuit operates as a synchronous transport, using<br />

a common timing source that <strong>the</strong> transmission equipment on both ends of <strong>the</strong> circuit<br />

use <strong>to</strong> derive timing. The first use of T-carrier transport was in 1962 <strong>to</strong> provide<br />

interoffice trunk links in major metropolitan areas. Until 1983, T1s were only used<br />

by <strong>the</strong> telephone system and <strong>the</strong> U.S. government. This was due <strong>to</strong> pre-divestiture<br />

pricing that based cost on <strong>the</strong> bandwidth of <strong>the</strong> circuit. After divestiture, T1 service<br />

pricing was tariffed and made available <strong>to</strong> <strong>the</strong> consumer market.<br />

It is rumored that T1 got its name from <strong>the</strong> fact that one mile (<strong>the</strong> distance between<br />

manholes in large cites) was <strong>the</strong> most reliable distance that could be supported<br />

between signal regenera<strong>to</strong>rs. Actually, <strong>the</strong> specification calls for 6,000 feet between<br />

repeaters, with <strong>the</strong> first leg and last leg of circuit being no more than 3,000 feet<br />

between <strong>the</strong> repeater and <strong>the</strong> termination point of <strong>the</strong> CO.

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