2. Definition of Cables and Wires
A Cable is two or more wire twisted/braided together to form one cable.this
wires are conductors that are covered with insulators to prevent
electrocution.This wires are used to transfer electricity from one device to
another.
3. Modem
A modem is a hardware device that connects the digital signals from a computer to an analog
telephone line. The sending modem modulates the data into a signal that is compatible with
the phone line, and the receiving modem demodulates the signal back into digital data for
the computer. This allows the signals to be transmitted longer distances than are normally
possible.
Modem speeds at different years are shown below.
• 300 bps - 1960s through 1983
• 1200 bps - 1984 and 1985
• 9600 bps - 1991
• 56 Kbps - 1998
• ADSL (up to 8 megabits per second (Mbps)) – 1999
Modems normally respond to any call made to them when connected to an outside line and
allow a connection. This may allow instant unsecured access to the network or the
computers. If the modem is not really required, it should be disabled or removed from
network work stations. If disabling the modem is not possible, it should be configured to
prevent auto-answer.
4. Hubs
A common connection point for devices in a network. Hubs are commonly
used to connect segments of a LAN. A hub contains multiple ports. When
a packet arrives at one port, it is copied to the other ports so that all
segments of the LAN can see all packets.
5. Switches
Also called a switching hub, it is used
to connect a device to another in a
computer network. It is considered as
a more advanced version of hubs since
it just sends a message to the device
that requests it rather than
broadcasting it to every port.
6. Servers
A server is a system (software and
suitable computer hardware) that responds
to requests across a computer network to
provide, or help to provide, a network
service. Servers can be run on a dedicated
computer, which is also often referred to as
"the server", but many networked
computers are capable of hosting servers.
In many cases, a computer can provide
several services and have several servers
running.
7. Routers A router is connected to two or more
data lines from different networks.
When a data packet comes in one of
the lines, the router reads the address
information in the packet to
determine its destination. Then, using
information in its routing table
or routing policy, it directs the packet
to the next network on its journey.
Routers perform the "traffic directing"
functions on the Internet.
