Appendix D. Glossary

CTS

clear to send. A signal on the DTE interface indicating that the DCE is clear to send data.

CV

code violation. Cyclic redundancy check (CRC) errors and frame bit errors when in ESF (extended super frame) format, or bipolar violations and frame bit errors when in SF (super frame) format.

data link See FDL.

dB

The standard abbreviation for decibel. A decibel is a unit of measure for signal. A decibel is usually the relation between a transmitted signal and a standard sig- nal source. Therefore, 6 dB of loss would mean that there is a 6 dB difference between what arrives down a communications circuit and what was transmitted by a standard signal generator.

DCE

data communications equipment. A device that provides all the functions required for connection to telephone company lines and for converting signals between telephone lines and DTE. Also see DTE.

DDS

digital data service. AT&T private line service for transmitting data over a digi- tal system. The digital transmission system transmits electrical signals directly, instead of translating the signals into tones of varied frequencies as with tradi- tional analog transmission systems. Digital techniques provide more efficient use of transmission facilities, resulting in lower error rates and costs than analog systems.

DE

discard eligibility. A user-set bit indicating that a frame may be discarded in preference to other frames if congestion occurs, to maintain the committed qual- ity of service within the network. Frames with the DE bit set are considered excess data.

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