Desktop Encyclopedia of Telecommunications, Second Edition
Explanations, not just definitions.
TABLE OF CONTENTS Desktop Encyclopedia of Telecommunications, Second Edition
T: T-Carrier Facilities Twisted-Pair Wiring
T-Carrier Facilities
T-carrier is a type of digital transmission system that is employed over copper, optical fiber, or microwave to achieve various channel capacities for the support of voice and data. The most popular T-carrier facility is T1, which is implemented by a system of copper wire cables, signal regenerators, and switches that provides a transmission rate of up to 1.544Mbps by using Digital Signal Level 1 (DS1). In Europe, the United Kingdom, Mexico, and other countries that abide by ITU standards, the equivalent facility is E1, which provides a transmission rate of 2.048Mbps.
T-carrier had its origins in the 1960s and was first used by telephone companies as the means of aggregating multiple voice channels onto a single, high-speed digital backbone facility between central-office switches. The most widely deployed T-carrier facility is T1, which has been commercially available since 1983.
Digital Signal Hierarchy
To achieve the DS1 transmission rate, selected cable pairs with digital signal regenerators (repeaters) are spaced approximately 6,000 feet apart. This combination yields a transmission rate of 1.544Mbps. By halving the distance between the span-line repeaters, the transmission rate can be doubled to 3.152Mbps, which is called DS1C. Adding more sophisticated electronics and/or multiplexing steps makes higher transmission rates possible, creating a range of digital signal levels as shown in the following table.
| North America | ||||
|---|---|---|---|---|
| Signal Level | Bit Rate | Channels | Carrier System | Typical Medium |
| DS0 | 64Kbps | 1 |
| Copper wire |
| DS1 | 1.544Mbps | 24 | T1 | Copper wire |
| DS1C | 3.152Mbps | 48 | T1C | Copper... |
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