ZyXEL Communications Prestige 724, User Manual

Page: 76 / 87

Prestige 724 G.SHDSL CSU/DSU
H Glossary
client. A web browser, for example, is a specific kind of client.
CO Central Office. A CO is a facility that serves local telephone subscribers. In the CO,
subscribers' lines are joined to switching equipment that allows them to connect to
each other for both local and long distance calls.
COE Central Office Equipment. COE is where home and office phone lines terminate and
connect to a much larger switching system.
CPE Customer Premise Equipment. CPE is privately-owned telecommunication equipment
at an organization’s site that is attached to the telecommunication network. CPE
includes routers, modems, PBXs, telephones, key systems, facsimile products, voice
processing equipment and video communication equipment.
Crossover
Ethernet Cable A cable that wires a pin to its opposite pin, for example, RX+ is wired to TX+. This
cable connects two similar devices, for example, two data terminal equipment (DTE)
or data communications equipment (DCE) devices.
CSU/DSU
Channel Service Unit/Data Service Unit. CSUs and DSUs are actually two separate
devices, but they are used in conjunction and often combined into the same box.
CSU/DSU are hardware devices that convert digital signals used on a LAN into a
digital signal used on a WAN and vice-versa (over a T-1 line, for example). These
devices are part of the hardware you need to connect computer equipment to digital
transmission lines. The CSU device connects with the digital communication line and
provides a termination for the digital signal. The DSU device, sometimes called a
digital service unit, is the hardware component you need to transmit digital data over
the hardware channel. This device converts signals from bridges, routers and
multiplexors into the bipolar digital signals used by the digital lines. Multiplexors mix
voice signals and data on the same line.
DCE Data Communications Equipment is typically a modem or other type of
communication device. The DCE sits between the DTE (data terminal equipment) and
a transmission circuit such as a phone line.
Digital The use of a binary code to represent information, such as 0/1, or on/off.
DLCI Data Link Connection Identifier. A DLCI specifies the channel and destination that
frame relay traffic will use.
DNS Domain Name System links names to IP addresses. When you access Web sites on
the Internet you can type the IP address of the site or the DNS name. When you type
a domain name in a Web browser a query is sent to the primary DNS server defined
in your Web browser’s configuration dialog box. The DNS server converts the name
you specified to an IP address and returns this address to your system. Thereafter, the
IP address is used in all subsequent communications.