（单词翻译:单击）
City Code - Some foreign countries require you to dial a city code before the phone number you are trying to reach.
Clamp - A circuit that removes the energy dispersal signal component1 from the video waveform.
Clarke Orbit - This is the circular orbit in space 22,237 miles from the surface of the earth at which geosynchronous satellites are placed to revolve2 around the earth. It is named after Arthur C. Clarke, who first postulated3 its existence. Satellites in these orbits move at speeds that cause their angular velocity4 to match the angular rate of the rotation5 of the earth, causing them to appear stationary6 when viewed from a particular point on Earth.
Clear to Send (CTS) - This is when a receiving modem7 tells the calling modem.
C/N (Carrier to Noise Ratio) - This is the carrier-to-noise-ratio, which is the ratio of the received carrier power to the noise power in a given bandwidth; it is expressed in decibels8 (dB), which is a logarithmic scale.
CO - See central office.
Codec - A coder/decoder system for transmitting digital data.
Color Subcarrier - A particular subcarrier that is added to the main video signal; its purpose is to convey the color information.
Columns - A column contains an item of data within a row.
Command - This is a software instruction that causes a specific job to be done.
Command Buffer9 - This is a memory place where commands are store temporarily.
Command Set - A collection of commands. (See Command.)
Commercial Internet (.com) - This is the part of the internet that is provided by commercial services, allowing business usage of the internet.
Common Carrier - Any organization which operates communications circuits used by other people. Common carriers include the telephone companies as well as communications satellite owners, AT&T and others.
Communication Channel - This is a type of circuit, and it is a two-way information pathway.
Communications Protocol10 - These are procedures used to ensure a standardized11 transmission occurs.
