3.2
Categorize standard connector types on network media
Just as the types of cable that we use have evolved over time,
so have the type of connectors. Some connectors have superseded others because
of their durability or ease of use. In this section, I will discuss the most
common connectors in use today.
Depending on whether you are using singlemode or multimode
fiber-optic cable and depending on the purpose of your connection, you may
choose from many different types of connectors. In this section, I will discuss
the most common fiber-optic connectors. You should be familiar with the
appearance and general purpose of each type of connector.
The straight tip (ST) connector uses a
half-twist bayonet type of lock to hold it in place securely. ST connectors are
most commonly used with singlemode fiber-optic cable that runs long distances.
It resembles a small BNC connector, but it's generally made of hard plastic.
Figure 3.8 shows an ST connector.
The standard connector (SC) connector is
a type of fiber-optic cable connector. It uses a push-pull connector mechanism
similar to common audio and video plugs. SC connectors are most often used with
multimode fiber-optic cable that is providing a backbone segment for a local
area network. Figure 3.9 shows an SC connector.
The local connector (LC) connector is a
fiber connector that is built into the body of an RJ-style jack. The LC
connector is perfect for local connections in an organization's telecom room or
network closet. Figure 3.10 shows an LC connector.
The mechanical transfer-registered jack (MTRJ) connector is
becoming more popular because of its compact size and durability. It contains
two fibers next to each other and resembles an RJ-45 connector. It was designed
to replace the SC connector and is less than half its size when you consider
that it provides two connected fibers instead of just one. Figure 3.11 shows an MT-RJ connector.
Not all connectors are fiber-optic connectors. In fact, we
still use a lot of copper connectors in our networks today. Some copper
connectors have “stood the test of time,” whereas others are rarely seen
anymore, but you might still have to know about them for the exam. In this section, I will
discuss the most common types of copper connectors and their general use.
The RJ-45 connector is the most common of
all network connectors. It is used to connect network interface cards (NICs) to
hubs and/or switches. RJ-45s can also be used to connect network devices
together for communication as well as control. The RJ-45 connector can contain
and connect four pairs of wires, although they generally connect only two pairs.
Figure 3.12 shows an RJ-45 connector.
Chances are very good that you have held an RJ-11 connector in your hand, since they are used on all the
telephone connections in the United States and most other countries. They can
contain and connect two pairs of wires. In regard to computers, you are most
likely to use an RJ-11 connector when you attach a modem to a telephone line in
the unlikely event you are still using a dial-up connection. I know there are
still some out there somewhere! Figure 3.13 shows an RJ-11 connector and jack.
Although this type of coaxial connector is rarely used in
today's networks, it is still listed as an item to recognize for the exam. Who knows, you might
run into one at some point if you “dig up” a very, very old network. The BNC connector is pushed in and then locked onto the
connection to hold it securely in place while connecting the core wire. Figure
3.14 shows a BNC connector.
The F-connector (Figure 3.15) is a coaxial type connector that is commonly used
with cable TV and cable modems. It will most likely be attached to an RG-6 or
RG-59 (in older installations) cable and will provide a solid connection to
facilitate the carrying of data or television signal.
The DB-9 or recommended standard 232
(RS-232) was a cable standard commonly used for serial data signals connecting
between data terminal and data communications equipment, such as when connecting
a computer's serial port to an external modem. As you can imagine, it is used
much less frequently today than it was in the past. Still, you should be able to
recognize a DE-9 female connector as one that might be used in an RS-232
connection. These types of connections are being superseded in today's networks
by more modern connectors such as USB. Figure 3.16 shows an RS-232 connector.
A patch panel is typically a rack or
wall-mounted structure that houses cable connections. A patch cable generally
plugs into the front side, while the back holds the punched-down connection of a
longer, more permanent cable. The purpose of the patch panel is to offer the
administrator a way to change the path of a signal quickly when needed. For
example, if a cable inside a wall becomes damaged or fails, a network
administrator can “patch around” that cable by simply changing the connection on
two patch panels. Figure 3.17 shows a modern patch panel.
A newer type of wiring distribution point, called a 110 block,
has replaced most telephone wire installations and is also being used for
computer networking. On one side of it, wires are punched down, while the other
side has RJ-11 (for phone) or RJ-45 (for network) connections. The 110 blocks
come in sizes from 25 to more than 500 wire pairs. Some are capable of carrying
1Gpbs connections when used with CAT6 cables. Figure 3.18 shows a 110 block.
The manner in which these wires are arranged is of extreme
importance. If you look inside a network cable, you will find four pairs of
wires. These wire pairs are twisted together to prevent crosstalk (as I
discussed earlier). Then the pairs of twisted wires are also twisted together to
help prevent EMI and tapping. You know that the same pins must be used on the
same colors throughout a network for receive and transmit, but how do you decide
which color wire goes with which pin? The good news is that you don't have to
decide--at least not completely. Two wiring standards have surfaced that have
been agreed upon by more than 60 vendors including AT&T, 3Com, and Cisco,
though there isn't 100 percent agreement in the industry. In other words, over
the years some network jacks have been pinned with the T568A standard, and some
have used the T568B standard. This can cause confusion if you don't know what
you are looking at in your network.
You may be thinking “What's the difference, and why does it
matter?” Well, the difference is the position of four wires on one side of the
cable--that's it! As you can see in Figure 3.19, pins 4, 5, 7, and 8 are not used at all in either
standard. This leaves only the wire pairs to connect to pins 1, 2, 3, and 6. If
you connect the green-white, green, orange-white, and orange wires to pins 1, 2,
3, and 6, respectively, on both sides of the cable, then you are said to be
using the 568A standard, and you would be creating a straight-through cable that
would be used as a regular patch cable for most networks. Note that the reason
for this is that most networks use the T568A standard for wall jacks. In essence
568A+568A= straight through and, 568B=568B=straight through, but
568A+568B=crossover. If, on the other hand, you switch from pin 1 to pin 3 and
from pin 2 to pin 6 on one side only, then you have created a crossover cable
for most networks.
Be familiar with the various fiber-optic
connectors There are multiple fiber-optic connectors that can be used in
various locations in your network. Know the main types of connectors and the
general build of each one. Also understand where each might be used and why it
might be advantageous over other options.
Be familiar with various copper connectors
There are multiple copper connectors that are used in your network. The most
common by far is the RJ-45 connector, which holds four pairs of wires, although
only two are generally used. Others include the RJ-11, BNC, DB-9, and
F-connector. Know the general build and use of each of these connectors.
Understand patch panels and 110 block
connectors Wiring distribution not only houses wiring connections but can
also provide an administrator with options for reconnects. Know the general
build and purpose of each of these
Just as the types of cable that we use have evolved over time,
so have the type of connectors. Some connectors have superseded others because
of their durability or ease of use. In this section, I will discuss the most
common connectors in use today.
Fiber
Depending on whether you are using singlemode or multimode
fiber-optic cable and depending on the purpose of your connection, you may
choose from many different types of connectors. In this section, I will discuss
the most common fiber-optic connectors. You should be familiar with the
appearance and general purpose of each type of connector.ST
The straight tip (ST) connector uses a
half-twist bayonet type of lock to hold it in place securely. ST connectors are
most commonly used with singlemode fiber-optic cable that runs long distances.
It resembles a small BNC connector, but it's generally made of hard plastic.
Figure 3.8 shows an ST connector. "Click To expand")
SC
The standard connector (SC) connector is
a type of fiber-optic cable connector. It uses a push-pull connector mechanism
similar to common audio and video plugs. SC connectors are most often used with
multimode fiber-optic cable that is providing a backbone segment for a local
area network. Figure 3.9 shows an SC connector. "Click To expand")
LC
The local connector (LC) connector is a
fiber connector that is built into the body of an RJ-style jack. The LC
connector is perfect for local connections in an organization's telecom room or
network closet. Figure 3.10 shows an LC connector.
MTRJ
The mechanical transfer-registered jack (MTRJ) connector is
becoming more popular because of its compact size and durability. It contains
two fibers next to each other and resembles an RJ-45 connector. It was designed
to replace the SC connector and is less than half its size when you consider
that it provides two connected fibers instead of just one. Figure 3.11 shows an MT-RJ connector.
Copper
Not all connectors are fiber-optic connectors. In fact, we
still use a lot of copper connectors in our networks today. Some copper
connectors have “stood the test of time,” whereas others are rarely seen
anymore, but you might still have to know about them for the exam. In this section, I will
discuss the most common types of copper connectors and their general use.RJ-45
The RJ-45 connector is the most common of
all network connectors. It is used to connect network interface cards (NICs) to
hubs and/or switches. RJ-45s can also be used to connect network devices
together for communication as well as control. The RJ-45 connector can contain
and connect four pairs of wires, although they generally connect only two pairs.
Figure 3.12 shows an RJ-45 connector.
RJ-11
Chances are very good that you have held an RJ-11 connector in your hand, since they are used on all the
telephone connections in the United States and most other countries. They can
contain and connect two pairs of wires. In regard to computers, you are most
likely to use an RJ-11 connector when you attach a modem to a telephone line in
the unlikely event you are still using a dial-up connection. I know there are
still some out there somewhere! Figure 3.13 shows an RJ-11 connector and jack.
BNC
Although this type of coaxial connector is rarely used in
today's networks, it is still listed as an item to recognize for the exam. Who knows, you might
run into one at some point if you “dig up” a very, very old network. The BNC connector is pushed in and then locked onto the
connection to hold it securely in place while connecting the core wire. Figure
3.14 shows a BNC connector. "Click To expand")
F-connector
The F-connector (Figure 3.15) is a coaxial type connector that is commonly used
with cable TV and cable modems. It will most likely be attached to an RG-6 or
RG-59 (in older installations) cable and will provide a solid connection to
facilitate the carrying of data or television signal.
DB-9 (RS-232)
The DB-9 or recommended standard 232
(RS-232) was a cable standard commonly used for serial data signals connecting
between data terminal and data communications equipment, such as when connecting
a computer's serial port to an external modem. As you can imagine, it is used
much less frequently today than it was in the past. Still, you should be able to
recognize a DE-9 female connector as one that might be used in an RS-232
connection. These types of connections are being superseded in today's networks
by more modern connectors such as USB. Figure 3.16 shows an RS-232 connector. "Click To expand")
Patch panel
A patch panel is typically a rack or
wall-mounted structure that houses cable connections. A patch cable generally
plugs into the front side, while the back holds the punched-down connection of a
longer, more permanent cable. The purpose of the patch panel is to offer the
administrator a way to change the path of a signal quickly when needed. For
example, if a cable inside a wall becomes damaged or fails, a network
administrator can “patch around” that cable by simply changing the connection on
two patch panels. Figure 3.17 shows a modern patch panel. "Click To expand")
block (T568A, T568B)
A newer type of wiring distribution point, called a 110 block,
has replaced most telephone wire installations and is also being used for
computer networking. On one side of it, wires are punched down, while the other
side has RJ-11 (for phone) or RJ-45 (for network) connections. The 110 blocks
come in sizes from 25 to more than 500 wire pairs. Some are capable of carrying
1Gpbs connections when used with CAT6 cables. Figure 3.18 shows a 110 block.
The manner in which these wires are arranged is of extreme
importance. If you look inside a network cable, you will find four pairs of
wires. These wire pairs are twisted together to prevent crosstalk (as I
discussed earlier). Then the pairs of twisted wires are also twisted together to
help prevent EMI and tapping. You know that the same pins must be used on the
same colors throughout a network for receive and transmit, but how do you decide
which color wire goes with which pin? The good news is that you don't have to
decide--at least not completely. Two wiring standards have surfaced that have
been agreed upon by more than 60 vendors including AT&T, 3Com, and Cisco,
though there isn't 100 percent agreement in the industry. In other words, over
the years some network jacks have been pinned with the T568A standard, and some
have used the T568B standard. This can cause confusion if you don't know what
you are looking at in your network.You may be thinking “What's the difference, and why does it
matter?” Well, the difference is the position of four wires on one side of the
cable--that's it! As you can see in Figure 3.19, pins 4, 5, 7, and 8 are not used at all in either
standard. This leaves only the wire pairs to connect to pins 1, 2, 3, and 6. If
you connect the green-white, green, orange-white, and orange wires to pins 1, 2,
3, and 6, respectively, on both sides of the cable, then you are said to be
using the 568A standard, and you would be creating a straight-through cable that
would be used as a regular patch cable for most networks. Note that the reason
for this is that most networks use the T568A standard for wall jacks. In essence
568A+568A= straight through and, 568B=568B=straight through, but
568A+568B=crossover. If, on the other hand, you switch from pin 1 to pin 3 and
from pin 2 to pin 6 on one side only, then you have created a crossover cable
for most networks. "Click To expand")
Exam Essentials
Be familiar with the various fiber-optic
connectors There are multiple fiber-optic connectors that can be used in
various locations in your network. Know the main types of connectors and the
general build of each one. Also understand where each might be used and why it
might be advantageous over other options.Be familiar with various copper connectors
There are multiple copper connectors that are used in your network. The most
common by far is the RJ-45 connector, which holds four pairs of wires, although
only two are generally used. Others include the RJ-11, BNC, DB-9, and
F-connector. Know the general build and use of each of these connectors.Understand patch panels and 110 block
connectors Wiring distribution not only houses wiring connections but can
also provide an administrator with options for reconnects. Know the general
build and purpose of each of these