ADTRAN Express 6120 Manual de instrucciones descargar pdf (Pagina 142)

Glossary

Glossary-2 Express 6100/6120 User Manual 61200176L1-1

Bridge

A data communications device that connects two or more networks.

Abridgestoresandforwardscompletepacketsbetweenthenetworks.

Bridges operate at the data-link layer of the OSI model.

CCITT

ConsultativeCommitteeonInternationalTelephony andTelegraphy.

A body of the International Telegraph Union (ITU) which prepares

recommendations, commonly referred to as international standards,

to resolve technical telegraph and telephone problems.

central office (CO)

In telephony, thephone company switching facility or center, usually

a Class 5 end office, at which subscribers local loops terminate. Han-

dlesaspecificgeographicarea,identifiedbythefirstthreedigitsofthe

local telephone number. Usually the facilities of the local BOC.

CSMA/CD

Carrier Sense Multiple Access Collision Detect. A channel access

mechanism wheredevices checkthe channel for acarrierbeforetrans-

mitting. If no carrieris sensed for the specified period of time, the de-

vice can transmit. If two devices transmit at once, a collision occurs

and is detected by all colliding devices. This collision subsequently

delays their retransmissionsfora random length oftime. CSMA/CD

is used by Ethernet and IEEE 802.3.

D-channel

The ISDN channel that carries signalling information to control the

call setup, teardown, orinvocation ofsupplementary services. The D-

Channel may also be used to provide packet mode data service.

DDS

Dataphone DigitalService. AT&Tprivatelineservicefortransmitting

data over a digital system. The digital transmission system transmits

electrical signals directly, instead of translating the signals into tones

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ADTRAN Express 6120 Manual de instrucciones Pagina 142