to describe the change in the slope of the curve between two sam- ples rather than the absolute change between the samples. CWDM (Coarse Wavelength Division Multiplexing) A WDM system that was specifi- cally developed for metro area applications. CWDM is based on the same principle as DWDM accommodating multiple wavelengths on a single fiber, but it uses less expensive lasers, making it cost-effective for metro deployments, cable TV, and enterprise networks. The tradeoff is that greater spacing is required between wavelengths, reducing the total number of wavelengths that can be supported. CXR (carrier) A signal of known characteristics (e.g., frequency) that is altered (i.e., modu- lated) to transmit information. cycle One complete repetition of a regularly repeating electronic function. The number of cycles per second, measured in Hertz (Hz), is called the frequency. DAB (Digital Audio Broadcasting) A standard that enjoys wide use in Europe for radio broadcasts. DAMA (demand assigned multiple access) A system for allocation of communication satellite time to earth stations as the need arises. dark fiber Fiber-optic cable that has been installed but is not lit (i.e., that has no active light sources). data center data center The computer-equipped, central location within an organization. The data cen- ter processes and converts information to a desired form such as reports or other types of man- agement information records. data circuit A communications facility that enables transmission of information in digital form. data communication The transmission and reception of data between computers and/or remote devices according to appropriate protocols. data compression and coding Techniques used to reduce bandwidth requirements for transmission of information over a particular communications link. These techniques may also be used in noncommunications applications, such as data storage and retrieval. data exchange The use of data by more than one program or system. data line privacy The evolving relationship betwe