Network Interface Cards/ISDN Adapters/System Area Network Cards
A NIC is everything its name suggests. It’s a “card”
inserted into a networked device that is used to create an interface with that
network. Look on the back of your computer and find where the RJ-45 (or whatever
media your network uses) is plugged into your computer. The point of contact is
your computer’s NIC. Most NICs are installed inside of the computer. PCs that
lack expansion slots (such as laptops) often use special adapters instead. For
instance, a PCMCIA
network adapter will connect a laptop to a network through the credit card-sized
PCMCIA expansion slot. A pocket adapter will connect a PC to a network through
its printer port.
How
to Install a NIC
Wireless Access Points
As the name suggests, wireless access points transmit network
signals to wireless client devices. The range of these signals varies, depending
on such variables as floors and walls. In general, the range is about 300 feet
in a building, up to 1000 feet in open air. In many ways, wireless access points
are like cellular phone towers. Wireless client PCs can "roam" through
and between access points, which extends the coverage area.
That understood, be careful not to misunderstand this: most
wireless access points cannot communicate with each other wirelessly. In
general, wireless access points communicate only with wireless clients. This is
especially true for cheap, consumer-grade products. This means that you can't
use two wireless access points to wirelessly connect two non-wireless LANs
together. To do this, you must use a wireless bridge, which takes you beyond the
scope of the Network+ exam. If you’d like to know more about wireless bridges
anyway, click here
for a very good article on the subject.
Wireless
Access Points and ARP Poisoning
Wireless
Access Points by c|net
Wirelessly
Connecting Two Wireless Access Points
Modems
A modem is a device that changes digital data into an analog
signal to be transmitted over analog medium, in most cases telephone lines, and
back again. You can see this in the name itself. Modem stands for MOdulator/DEModulator.
There are three types of modems you should know about:
- Traditional (POTS/PSTN)
This is the type installed in, or (less and less commonly) attached
externally to most computers today. This type converts signals to transmit
over POTS/PSTN lines and back again to communicate with the computer itself.
These modems are common simply because manufacturers place one in
practically every computer, though they are not necessarily the best
available. The top speed rating is 56 Kbps. In reality, the top
transfer rate is only 53.3 Kbps owing to the characteristics of analogue
telephone communications.
Click here
to view a typical internal 56K Modem
- DSL (Digital Subscriber Line)
This high-speed technology is becoming increasingly popular, especially in
business and industry where fast access can be vital. Unlike the traditional
modem, a DSL line can remain connected to the Internet indefinitely. This
means connections are constantly available ("always-on"). Typical
download rates with DSL are up to 1.544 Mbps, while upload rates are as high
as 128 Kbps (the a in aDSL stands for asymmetric and refers to this
difference).
DSL uses multiple channels in higher frequency ranges (more than 3200Hz)
than regular voice phone calls, which means greater bandwidth than
traditional modems. A DSL line can carry both voice and data, so you don't
have to install a separate phone line. DSL service can be established on
existing lines, so long as the service is available and you are within the
specified distance from the telephone company's central switching office or
booster station. It does require a special modem installed in the computer.
Prices for equipment, installation and monthly service vary a great deal,
though prices have dropped recently.
A reminder: if you have DSL service on the same service line used to make
voice calls, install DSL filters on all the telephone devices. Otherwise,
callers will hear a very annoying hissing noise (which is how DSL signals
sound) during voice calls.
The
Fast Guide to DSL.
- Cable Modems
These modems provide high-speed Internet access via cable television lines.
At speeds of up to 36 Mbps, cable modems can download in seconds data that
might require many times longer with a 56K dial-up connection. Since it
works over TV cable, it won’t tie up a telephone line and it is available
continuously. This means no need to make a connection and no busy signals.
A downside to cable is that access and bandwidth are shared by several to
many customers in a loop—this can be a security issue, and can mean
lowered transmission rates if everyone in the loop is active simultaneously.
Cable-Modems.org.