电信专业英英词典C-2

（单词翻译:单击）

　　Cassegrain Antenna¹ - An antenna that places a subreflector at the focal point to reflect energy to or from a feed located at the apex² 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 interfering³ 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 determined⁴ 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 modems⁵.

　　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 simultaneously⁶ on the same frequency. This technique effectively doubles the channel carrying capacity of the satellite.