Page 115 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Exposure to Computer Disciplines

Notes 6.2.2.1 ISDN Lines
ISDN stands for Integrated Services Digital Network. It is a set of standards used for digital
transmission over telephone line. The ISDN uses the multiplexing technique to carry three or
more data signals at once through the telephone line. It is because the data transmission speed
of ISDN line is very fast. In ISDN line, both ends of connections require the ISDN modem and
a special telephone set for voice communication. Its data transmission speed is up to 128 Kbps.
6.2.2.2 DSL

DSL stands for Digital Subscriber Line. It is another digital line. In DSL, both ends of
connections require the network cards and DSL modems for data communication. The data
transmission speed and other functions are similar as ISDN line. DSL transmits data on existing
standard copper telephone wiring. Some DSLs provide a dial tone, which allows both voice
and data communication.
6.2.2.3 ADSL

The ADSL (Asymmetric Digital Subscriber Line) is another digital connection. It is faster
than DSL. ADSL is much easier to install and provides much faster data transfer rate. Its data
transmission speed is from 128 Kbps up to 10 tvlbps. This connection is ideal for Internet access.

6.2.2.4 Cable Television Line
The Cable Television (CATV) line is not a standard telephone line. It is a dedicated line used
to access the Internet. Its data transmission speed is 128 Kbps to 3 Mbps.
A cable, modem is used with the CATV it provides a high speed Internet connections through
the cable television network. A cable modem sends and receives digital data over the cable
television network.
To access the Internet using the CATV network, the CATV Company installs a splitter inside
your house. From the splitter, one part of the cable runs to your television and other part
connects to the cable modem. A cable modem usually is an external device, in which one end
of a cable connects to a CATV wall outlet while the other end plugs into a port (such as on
an Ethernet card) in the system unit.

6.2.2.5 T-Carrier Lines
It is very fast digital line that can carry multiple signals over a single communication
line whereas a standard dialup telephone line carries only one signal. 1-carrier lines use
multiplexing so that multiple signals share the line. T-carrier lines provide very fast data
transfer rates. The T-carrier lines are very expensive and large companies can afford these
lines. The most popular T-carrier lines are:
(i) T1 Line
(ii) T3 Line
T1 Line The most popular 1-carrier line is the Ti line (dedicated line). Its data transmission
speed is 1.5 Mbps. Many ISPs use Ti, lines to connect to the Internet backbone. Another type
of TI line is the fractional TI line. It is slower than TI line but it is less expensive. The home
and business users use this line to connect to the Internet and share a connection to the Ti
line with other users.

Businesses often use T1 lines to connect to the Internet.

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