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Glossary

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Term Main definition
Central office (CO)

The telephone company building where subscribers

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Central office ground bus

Essentially a large ground bar used in a central office to provide a centralized grounding for all the equipment in that CO (or even just a floor in that CO).

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Channel

The end-to-end transmission or communications path over which application-specific equipment is connected. Through multiplexing several channels, voice channels can be transmitted over an optical channel.

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Channel bank

Equipment that combines a number of voice and sometimes digital channels into a digital signal; in the case of a T-1 channel bank, it converts 24 separate voice channels into a single digital signal.

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Channel insertion loss

The static signal loss of a link between a transmitter and receiver for both copper and fiber systems. It includes the signal loss of the cable, connectors/splices and patch cords.

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Channel service unit/digital service unit (CSU/DSU)

A hardware device that is similar to a modem that connects routers

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Characteristic impedance

The impedance that an infinitely long transmission line would have at its input terminal. If a transmission line is terminated in its characteristic impedance, it will appear (electrically) to be infinitely long, thus minimizing signal reflections from the end of the line.

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Cheapernet

A nickname for thin Ethernet (thinnet) or 10Base-2 Ethernet systems.

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Cheater bracket

A bracket used for making cable installation easier.

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Chromatic dispersion

The spreading of a particular light pulse because of the varying refraction rates of the different colored wavelengths. Different wavelengths travel along an optical medium at different speeds. Wavelengths reach the end of the medium at different times, causing the light pulse to spread. This chromatic dispersion is expressed in picoseconds per kilometer per nanometer (of bandwidth). It is the sum of material and waveguide dispersions. See also waveguide dispersion, material dispersion.

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Churn

Cabling slang for the continual rearrangement of the various connections in a data connection frame. Office environments where network equipment and phones are frequently moved will experience a high churn rate.

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Circuit

A communications path between two pieces of associated equipment.

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Cladding

Name for the material (usually glass, sometimes plastic) that is put around the core of an optical fiber during manufacture. The cladding is not designed to carry light, but it has a slightly lower index of refraction than the core, which causes the transmitted light to travel down the core. The interface between the core and the cladding creates the mode field diameter, wherein the light is actually held reflectively captive within the core.

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Cladding mode

A mode of light that propagates through and is confined to the cladding.

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Class A

(1) ISO/IEC 11801 channel designation utilizing twistedpair cabling rated to 100KHz. Used in voice and low-frequency applications. Comparable to TIA/EIA Category 1 cabling; not suitable for networking applications. (2) IP addresses that have a range of numbers from 1 through 127 in the first octet.

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