电信专业英英词典C-2_电脑电信

　cassegrain antenna - an antenna that places a subreflector at the focal point to reflect energy to or from a feed located at the apex of the main reflector.

　cb - this stands for citizen's band and is low-power (up to 4 watts), public radio that does not require fcc approval.

　cd - see carrier detect.

　cdma - this stands for code division multiple access and refers to a multiple-access scheme where stations use wide-spectrum modulations and orthogonal codes to reduce the chance of interfering with each other.

　central office (co) - this is a place where lines are joined to switching equipment (which control connections).

　channel - a frequency band, 6 mhz wide in the us, in which a specific broadcast signal is transmitted. channel frequencies are determined in the us by the federal communications commission (fcc).

　character - this is a letter, numeral, or symbol.

　characters per second (cps) - this is the number of characters that can be sent over the phone lines in 1 second.

　chat - a mode that allows two or more people to communicate with each other in real time over a network using modems.

　checksum - this is the sum of a group of data items that is used for error checking. received information packets must have the same number of bits present during the initial transmission.

　chip - this is the physical structure of an integrated circuit.

　circuit - this is an electrical device that provides a path for electrical current to flow, or more generally, it is a journey or route all the way around a particular place or area.

　circular polarization - some satellites transmit both right-hand rotating and left-hand rotating signals simultaneously on the same frequency. this technique effectively doubles the channel carrying capacity of the satellite.