T W E N T Y - T W O
C H A P T E R
BUILDING TELECOMMUNICATION
SYSTEMS
22.1 TELECOMMUNICATION SYSTEMS
Historical Perspective
Methods of communicating over long distances have evolved
over many millennia. Although carrier pigeons were used to
convey messages from about 700 B.C.E., the first long-distance
communication systems were based on signals of sound and
light (e.g. drums and horns, smoke signals and beacon fires).
Signal fires alerted the British of the arrival of the Spanish
Armada in 1588 C.E. The Chinese used rockets as signals to
warn of an imminent attack on the Great Wall. Native Americans
communicated by covering and uncovering a bonfire with a
blanket to produce smoke signals or by beating drums. The
British Navy sent signals at night by raising and lowering a
lantern, which coincidentally was the same way Paul Revere
was signaled with news of the arrival of the British. In
instances when clear vision was difficult (e.g., fog), bells or
whistles and fired weapons sent signals. Until almost 1800,
traditional long-distance communication was by horse-mounted
dispatch riders.
In 1793 Frenchman Claude Chappe developed an optical
telegraph (semaphore) system of stations built on rooftops or
towers that were visible from a great distance. Each semaphore
station consisted of a column-like tower with a moveable beam.
Attached to the beam were two moveable arms. The beam and
arms were swiveled with ropes, conveying different signal patterns representing upper- and lowercase letters, punctuation
marks, and numbers. A set of patterns was translated into words
by an observer at another station, who then sent it on to the next
station. This system allowed the French to send a concise message over 100 miles (160 km) in less than 5 min as long as visibility was good. Swede A. N. Edelcrantz developed another
type of optical telegraph system with ten collapsible iron shutters, which when placed in various positions formed combinations of numbers that were translated into letters, words, or
phrases. Crude semaphore systems were also used in Boston,
New York City, and San Francisco at that time.
Communications by sending electrical signals over wires
came only after the demonstration of electromagnetism by
Danish physicist Christian Oersted in 1820 and electrical flow
by Michael Faraday and others before him. In 1830, American
Joseph Henry transmitted the first practical electrical signal by
sending electricity through a long set of wires to produce electromagnetism that was used to ring a bell. The next year, in
1831, American, Samuel Morse patented the first functional
electrical communication system: the electric telegraph with its
system of electrical impulses identified as dots and dashes that
eventually became known as Morse Code.
The first message sent by electric telegraph was “What
hath God wrought,” from the Supreme Court Room in the U.S.
Capitol to the railway depot at Baltimore on May 24, 1844.
Three decades later, in 1861, there were over 2000 telegraph offices in operation across America and the East and West coasts
were connected. Six years later, the first transatlantic cable was
laid, connecting England and the United States. The telegraph
flourished as a method of long-distance communication throughout the world.
On March 10, 1876, in Boston, Massachusetts, Alexander
Graham Bell invented an electrical speech machine that transmitted voice over wires and became known as the telephone.
Bell’s assistant, Thomas Watson, fashioned the device from a
funnel, a cup of acid, and copper wire attached to a wooden
stand. “Mr. Watson, come here, I want you!” were the first
words accidentally spoken into the new invention. Four years
later in 1880, the first telephone company, American Bell, was
formed and over 30 000 phones were in use. Within 40 years
(about 1920), over ten million American Bell System telephones
were in service.
In 1895, Italian inventor Gugliemo Marconi demonstrated the first radio transmission that was received out of a
line of sight (about 2 miles) on the grounds of his family estate
in Italy. Six years later in Newfoundland, Canada, Marconi’s
radio received a weak signal that was sent across the Atlantic
Ocean by one of his associates in Cornwall, England. The signal was an “S” sent in Morse Code format, “dot, dot, dot.” It
demonstrated that radio waves could bounce off the upper atmosphere. The first true radio message was sent a year later.
Less than 50 years after the telephone was invented, transatlantic communications from New York to London became operational with signals transmitted by radio waves.
In 1865, Italian physicist Giovanni Caselli invented a
pantelegraph for transmitting pictures, the first commercial fax
system. On May 19, 1924, the first transmission of pictures
over telephone wires was publicly demonstrated. On January
23, 1926, John Logie Baird of Scotland gave the first public
demonstration of a mechanical television with images of living
human faces, not just outlines or silhouettes. It was with this
use of radio waves that transmission of pictures took a major
step toward the television we use today.
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CHAPTER 22
New engineering and scientific discoveries continued during the last half of the twentieth century with the gradual introduction of automatic switching devices, Teletype machines,
transatlantic cables, microwave and fiber optic technologies, communications satellites (e.g., Telstar I in 1962), personal computers, fax machines, wireless (cellular) phone service, and the
Internet. Today’s telecommunications industry includes simple
voice telephone calls, fax transmissions, video conferencing,
cable TV, access to the Internet, high-speed data communications,
satellite communications, and surfing the World Wide Web.
Fundamentals of
Telecommunications Systems
By industry definition, telecommunication is the transmission,
emission, or reception of signs, signals, writing, images,
sounds, or information of any nature by wire, radio, optical, or
other electromagnetic systems. A telecommunication system
uses electricity, light (visible and infrared), or radio waves to
transmit signals that carry voice and data transmissions.
Telecommunication systems function when a transmitter
converts sound waves (e.g., those created when a person speaks
into a telephone mouthpiece) or data into signals, which travel
along wires or through the air before reaching their destination.
When a receiver intercepts the signals, they are converted back
into useful data or sound waves that become distinguishable by the
human ear and recognized by brain. A transceiver is a telecommunications device that functions as a transmitter and receiver.
Historically, telecommunications systems such as a telephone system have used analog transmission. Modern systems
use digital transmission technology. The following is a description of these transmission formats:
Telecommunication Networks
A telecommunications network is a collection of communication equipment and devices that are interconnected so they can
communicate in order to share data, hardware, and software or
perform an electronic function. The network includes a series
of connecting points called nodes (e.g., a telecommunication
terminal such as a telephone receiver or computer) that are interconnected with cables (wiring). Networks can also interconnect with other networks and contain subnetworks.
In design and layout of communication networks, the
term topology describes the configuration of a network, including its nodes, connecting cables and equipment. It describes the
manner in which the cable is run to individual workstations on
the network. As shown in Figure 22.1, there are three basic network topologies: the bus, the star, and the ring. Acronyms and
abbreviations used in the telecommunications industry are
shown in Table 22.1.
Analog transmission in an electronic network is the conversion of useful sound or data into electrical impulses. It
is capable of transmitting both voice and nonvoice messages (e.g., telex, telegrams, data). However, nonvoice
transmissions are bulky when transmitted in an analog
format, so they cannot be transmitted rapidly.
Digital transmission in an electronic network involves a
transmission of a signal that varies in voltage to represent
one of two separate states (e.g., on and off or 0 and 1). In
an optical network, digital signaling can involve either
pulsating (on and off) light or a variation in the intensity
of the light signal. Digital transmission over radio systems (microwave, cellular, or satellite) can be accomplished by varying the amplitude of the wave. Digital
transmission technology offers a rapid method of voice
and nonvoice transmission.
In telecommunications systems, bandwidth is the range
between the highest and lowest frequencies of transmission,
measured in hertz (Hz), cycles per second. Bandwidth varies
with the type and method of transmission. It is a measure of the
information capacity.
FIGURE 22.1 The basic network topologies used in building
telecommunication systems: the bus, the ring, and the star.
TABLE 22.1
ACRONYMS AND ABBREVIATIONS USED IN THE TELECOMMUNICATIONS INDUSTRY.
ACR
Attenuation to cross-talk ratio
m
Meter
ANSI
American National Standards Institute
MAC
Media access control (layer)
ASTM
American Society for Testing and Materials
MAC(s)
Moves, adds, and changes
ATM
Asynchronous transfer mode
MAU
Medium attachment unit
AUI
Attachment unit interface
Mbs
Megabits per second
AWG
American Wire Gauge
MC
Main cross-connect
BER
Bit error rate
MDF
Main distribution frame
BICSI
Building Industry Consulting Service International
MHz
Megahertz
CCITT
International Telegraph and Telephone Consultative
Committee
mm
Millimeter
NBC
National Building Code
COAX
Coaxial cable
NEC
National Electrical Code
COSAC
Canadian Open Systems Application Criteria
NEMA
National Electrical Manufacturers Association
CSA
Canadian Standards Association
NeXT
Near-end cross-talk
CSMA/CD
Carrier sense multiple access/collision detection
EF
Entrance facility
EIA
Electronic Industries Association
EMI
Electromagnetic interference
EMI
Electrical metallic tubing
EP
Entrance point
ER
Equipment room
Ethernet
Precursor to, and almost identical with, the IEEE802.3
standard
FDDI
Fiber distributed data interface
FIPS PUB
Federal Information Processing Standard Publication
FTE
Field test equipment
HC
Horizontal cross-connect
HVAC
Heating, ventilation, and air conditioning
Hz
Hertz
IC
Intermediate cross-connect
IDC
Insulation displacement contact
IEC
International Electro-Technical Commission
IEEE
Institute of Electrical and Electronics Engineers
NI
Network interface
NIR
Near-end cross-talk to insertion loss ratio
NIST
National Institute of Standards and Technology
nm
Nanometer
NRZ
Nonreturn to zero
OSI
Open systems interconnection
PBX
Private branch exchange
PVC
Polyvinyl chloride
PWA
Provisioned work area
RCDD
Registered communications distribution designer
RFI
Radio frequency interference
ROI
Return on investment
SQL
Structured query language
STP
Shielded twisted pair
TBITS
Treasury Board Information Technology Standard
TC
Telecommunications closet
TIA
Telecommunications Industry Association
TO
Telecommunications outlet
TP/PMD
Twisted pair/physical media dependent
TR
Token Ring
TSB
Telecommunications System Bulletin
ISDN
Integrated services digital network
ISO
International Organization for Standardization
ITU
International Telecommunications Union—
Telecommunications Standardization Section
UTP
Unshielded twisted pair
kHz
Kilohertz
UL
Underwriters Laboratories, Inc.
km
Kilometer
WA
Work area
LAN
Local area network
WAN
Wide area network
LED
Light emitting diode
X
Cross-connect
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A bus topology connects each workstation (node) to a
single cable trunk. All signals are broadcast to all workstations.
Each computer checks the address on the signal as it passes
along the bus. If the signal’s address matches that of the computer, the computer processes the signal. If the address does not
match, the computer takes no action and the signal travels down
the bus to the next computer. Next, in a star topology, all workstations (nodes) are connected to a central unit called a hub.
Home runs are cables that extend from the hub to the terminal
without splicing or other connections. This configuration
allows cables to have a direct link between entrance facilities/
equipment room equipment, telecommunications closet devices,
and workstation equipment (e.g., computers, printers, telephone
receiver, and so on). Third, a network that is wired in the ring
topology connects workstation equipment and devices in a pointto-point serial manner in an unbroken circular configuration.
Not all networks are the same. The various types
provide different services, use different technology, have different resources and require users to follow different procedures. Networks can be distinguished in terms of spatial
distance between nodes such as local area networks (LAN),
metropolitan area networks (MAW), and wide area networks
(WAN). Large telephone networks and networks using their
infrastructure (such as the Internet) have sharing and exchange arrangements with other companies so that large
WANs are created. In building telecommunication systems,
LANs are used. LANs connect computers and hardware such
as printers located relatively close together and sharing
resources, equipment, and files. Types of LANs include the
Ethernet, ARCnet, and Token Ring, each having their own
method of transmitting data.
The transmitting medium used in networks can be copper
wire, glass, or plastic (fiber optic cable), and air (microwave
and radio wave). A signal sent through a telecommunications
network can be sent through any or all of these media.
Transmission Media
Cable is the most common medium through which voice and
data usually move from one network device to another. It serves
as the pipeline of a telecommunication system. There are several types of cable in use, including copper wire, coaxial cable,
and optical fibers. Copper wiring used in building telecommunication transmission is being replaced by optical fibers because they have much greater signal capacity. Wireless
transmission capabilities are also used in buildings and are replacing the need for hard-wired direct connections.
Connectors are the devices that connect cable to the network device (e.g., computer, printer, entertainment center, and
so forth). Connectors may come with the equipment purchased
or it may be necessary to purchase them individually. Connections on a cable system tend to be the weakest element in any
network, so they must be made properly.
CHAPTER 22
Types of transmission media include the following.
Copper Wiring
Historically, copper wiring has been the principal telecommunications transmission medium. It consists of one or more pairs
of solid copper wires. Bundles of pairs of twisted insulated copper wires form the majority of the telephone lines in the United
States and elsewhere. See Photo 22.1.
Twisted pair cable consists of pairs of copper wires that
are twisted to certain specifications. Each pair is twisted with a
specified number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices; the
tighter the twisting, the higher the supported transmission rate
but the greater the cost. Each signal on a twisted pair requires
both wires. Because some telephone sets or desktop locations
require multiple connections, a twisted pair is sometimes installed in two or more pairs, all within a single cable. Typically,
twisted pair cable has four pairs of wires inside the jacket.
Twisted pair comes with each pair uniquely color coded when
it is packaged in multiple pairs.
Twisted pair wiring is available in shielded and unshielded versions. Unshielded twisted pair (UTP) wiring consists of multiple pairs of twisted insulated copper conductors
bound in a single sheath. It is unshielded from electromagnetic
waves and therefore is sensitive to electrical interference. UTP
wiring is adequate for basic voice, fax, or data communications. For some applications, a twisted pair is enclosed in a
shield and is known as shielded twisted pair (STP) wiring. An
outer covering or shield is added to the ordinary twisted pair
wires; the shield functions as a ground. STP is suitable for environments with electrical interference; however, the extra
shielding can make the cables quite bulky. Thus, the more common type of wire used is not shielded. STP is commonly used
in Token Ring networks and UTP in Ethernet networks, where
it is referred to as 10baseT.
The quality of UTP will vary from telephone grade to extremely high-speed cable. The Telecommunications Industry
Association (TIA), an offshoot of the Electronic Industries
PHOTO 22.1 Twisted pair copper cable. (Used with permission
of ABC)
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BUILDING TELECOMMUNICATION SYSTEMS
TABLE 22.2
ANSI/TIA/EIA STANDARD 568 CATEGORIES (CAT) OF TWISTED PAIR CABLING.
Category
Maximum Data Rate
Usual Application
CAT 1
Less than 1 Mbps
Used for basic voice telecommunications (e.g., telephone, intercom) and limited power circuit cables
(e.g., alarm and doorbell wiring).
Not suitable for networking applications.
CAT 2
4 Mbps
Mainly used in the IBM cabling system for Token Ring networks.
CAT 3
16 Mbps
Used in low-speed data applications, primarily for telephone wiring and 10BaseT Ethernet.
CAT 4
20 Mbps
Rarely used. Primarily for Token-Ring networks.
CAT 5
100 Mbps
1000 Mbps (4 pair)
CAT 5e
100 Mbps
Provides optimal performance for all data and phone systems and has become the standard for
high-speed applications. Will run with peak accuracy, efficiency, and throughput. Primarily for 10BaseT
Ethernet, and 100BaseT Ethernet.
CAT 6
Up to 250 Mbps
Extremely fast broadband applications.
CAT 7
Up to 600 Mbps
Super-fast broadband applications.
Association (EIA), has established TIA/EIA standards of UTP
and rated categories of wire as shown in Table 22.2.
In addition to the EIA/TIA standards, the U.S. standard
for wire conductor size applied to copper electrical power and
telephone wiring is American Wire Gauge (AWG). The gauge
refers to wire thickness: the higher the gauge number, the thinner the wire. Wiring used for typical household power circuiting is AWG 14 or 12, greater on circuits serving large equipment.
Telecommunications wire is thinner, typically AWG 22, 24, or
26. Because thicker wire carries current more efficiently
(because it has less electrical resistance over a specific length), a
thicker wire is more efficient for longer distances. For this reason, where extended distance is required, a company installing
a network might prefer telephone wire with the lower gauge,
thicker wire of AWG 22. 22 AWG wire is typically used in telephone and UTP wire.
RJ45 connectors are the standard female connectors used
in a telecommunication system for UTP cable. A slot allows the
RJ-45 to be inserted only one way. RJ stands for registered
jack, implying that the connector follows a standard borrowed
from the telephone industry. The RJ45 is an eight-pin connector
used for data transmission or networking and some business
telephones. Pins are numbered 1 through 8 with a locking clip
at the top. Telephone connectors, referred to as RJ11 or RJ12,
have four or six pins, respectively.
Coaxial Cable
Coaxial cable has two conductors: an inner solid wire surrounded by an outer braided metal sheath. The conductors both
run concentrically along the same axis; thus the name coaxial
(COAX). Insulation separates the two concentric conductors,
and a hard casing protects the entire cable. Several coaxial cables can be arranged in bundles protected by an outer sheathing, called a jacket.
The primary types of coaxial cabling are as follows:
Thin coaxial cable is also referred to as thinnet. Thinnet
is about 1⁄4 inch (8 mm) in diameter and is very flexible. It
looks like regular TV cable. The 10Base2 designation
refers to specifications for thin coaxial cable. The 2 refers
to the approximate maximum segment length being 200 m
(654 ft), but the maximum practical segment length is
actually 185 m (605 ft).
Thick coaxial cable is referred to as thicknet. 10Base5
refers to the specifications for thick coaxial cable. The 5
refers to the maximum segment length being 500 m
(1635 ft). Thick coaxial cable has an extra protective
plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a better choice
when running longer lengths in a linear network. A disadvantage of thick coaxial is that it does not bend easily and
is difficult to install. Thicknet is not commonly used except as a backbone within and between buildings.
Triax cable is a type of coax cable with an additional
outer copper braid insulated from signal carrying conductors. It has a core conductor and two concentric conductive shields.
Twin axial cable (Twinax) is a type of communication
transmission cable consisting of two center conductors
surrounded by an insulating spacer, which in turn is surrounded by a tubular outer conductor (usually a braid,
foil, or both). The entire assembly is then covered with an
insulating and protective outer layer. It is similar to coaxial cable except that there are two conductors at the center.
Common types of coaxial cable are shown in Table 22.3.
Coaxial cable is very effective at carrying many analog
signals at high frequencies. In contrast to twisted pair wires,
coaxial has a much higher bandwidth to carry more data, and
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CHAPTER 22
TABLE 22.3
Cable Type
COMMON TYPES OF AXIAL CABLE.
Illustration
Description
Coaxial cable
Coaxial cables are constructed with an inner conductor surrounded
by a dielectric, which is enclosed by an outer conductor that also
acts as a shield. A protective jacket covers the outer conductor and
also acts as insulation.
Dual-shielded coaxial cable
Dual-shielded coaxial cables have two outer conductors, or shields,
enclosing the dielectric. Dual shielding is needed for strength and
abrasion resistance. Offers a decrease in attenuation and the
possibility of unwanted external signals.
Twin axial cable
Twin axial cable is composed of two insulated single conductor
cables or hook-up wires twisted together, having a common shield
and protective jacket.
Triaxial cable
Triaxial cable is coaxial cable with one inner conductor and two
shields all separated with dielectric material. Triaxial cable signals
may be transported by both the inner conductor and the inner shield
while the outer shield is at ground potential.
offers greater protection from noise and interference. Although
coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths
between network devices than twisted pair copper cable.
High-capacity coaxial cable is widely used in cable television systems because it is capable of carrying many TV and
radio signals simultaneously. Coaxial cable is used by telephone and cable television companies from the central office to
the user. It is also widely installed for use in business and
school LANs. Gradually, existing coaxial lines are being replaced by optical fibers.
The most common type of connector used with coaxial
cables is the Bayonet Neil-Concelman (BNC) connector. A
BNC male connector has a pin that connects to the primary
conducting (core) wire and then is locked in place with an outer
ring that turns into locked position. Different types of adapters
are available for BNC connectors, including a T-connector, barrel connector, and terminator.
Optical Fibers
Optical fibers are long, thin strands of very pure silicon glass or
plastic about the diameter of a human hair. A single optical fiber
consists of three elements: a core, the thin glass center of the
fiber where the light travels; cladding, the outer material surrounding the core that reflects the light back into the core; and a
buffer coating, a plastic coating that protects the fiber from damage and moisture. Each strand can pass a signal in only one direction, so fiber optic cable on a network typically consists of at
least two strands: one for sending and one for receiving.
Hundreds or thousands of optical fibers are arranged in
bundles called optical cables. The cable’s outer sheathing,
called a jacket, protects these bundles. Optical fibers come in
two types: single-mode fibers that are used to transmit one
signal per fiber (used in telephones and cable TV); and
multimode fibers that are used to transmit many signals per
fiber (used in computer networks, local area networks).
The most common connectors used with fiber optic cable
are the ST and SC connectors. The ST connector is barrel
shaped, similar to a BNC connector. The SC connector has a
squared face and is easier to connect in a confined space.
Optical fiber carries much more information than copper
wire and is in general not subject to electromagnetic interference. This makes it ideal for environments that contain a large
amount of electrical interference. This characteristic has made
it the standard transmission medium for connecting networks
between buildings.
Fiber optics refers to the technology in which communication signals in the form of modulated light beams are transmitted over a glass fiber transmission medium. The light in a
single optical fiber travels through the core by reflecting from
the mirror-like cladding, a physical principle called total internal reflection. Light reflects from the cladding no matter what
angle the fiber itself is bent. Because the cladding does not absorb any light from the core, the light wave can travel great distances. Light is generated by a laser or a light-emitting diode
(LED). Lasers have more power than LEDs, but vary light output more with changes in temperature and are more expensive.
A fiber optic relay system transmits and receives a light
signal that is transmitted through an optical fiber. An optical
transmitter produces and encodes the light signal that is sent
through the optical fiber. An optical receiver that decodes the
signal receives the light signal. The receiver uses a photocell or
photodiode to detect the light signal, decodes it, and sends an
electrical signal to a computer, TV, or telephone. Over long distances, an optical regenerator is needed to boost the light signal.
One or more optical regenerators may be spliced along a long
cable to amplify the degraded light signal.
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BUILDING TELECOMMUNICATION SYSTEMS
TABLE 22.4
COMMON TYPES OF ETHERNET CABLE IN USE.
Maximum
Distances
Cable Type
Specification
Meters
Feet
Unshielded twisted pair
Thin coaxial
Thick coaxial
Fiberoptic
Unshielded twisted pair
Unshielded twisted pair
10BaseT
10Base2
10Base5
10BaseF
100BaseT
100BaseTX
100
185
500
2000
100
220
325
600
1635
6540
325
719
The most common wavelengths of light signals in a fiber
optic system are 850 nm, 1300 nm, and 1550 nm, which are
all wavelengths within the nonvisible, infrared area of the electromagnetic light spectrum. Single-mode fibers have small
cores (about 0.00035 in or 9 !m diameter) while multimode
fibers have larger cores (about 0.0025 in or 62.5 !m diameter).
Optical fibers made from plastic require a much larger core
(0.04 in or 1 mm diameter) and transmit visible red light
(wavelength " 650 nm) from LEDs.
As light passes through the optical fiber, the light signal
degrades over its length. Degradation is principally caused by
impurities in the glass or plastic. The extent that the signal degrades depends on the purity of the medium and the wavelength
of the transmitted light (e.g., higher wavelengths tend to have
less degradation). The finest optical fibers offer signal degradation of less than 10% per km at wavelengths 1550 nm.
Fiber optic cable has the ability to transmit signals over
much longer distances than coaxial and twisted pair cabling and
can carry information at much greater speeds. This capacity
broadens communication possibilities to include services such
as video conferencing and interactive services. The cost of fiber
optic cabling is comparable to copper cabling; however, it is
more difficult to install and modify. 10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals. Common types of Ethernet cable in use are shown in Table 22.4.
Wireless
Wireless is a term used to describe telecommunications in
which electromagnetic waves (instead of some form of wire)
carry the signal. Wireless communications can take several
forms: microwave, synchronous satellites, low-earth-orbit
satellites, cellular, and personal communications service (PCS).
In every case, a wireless system eliminates the need for a complex hard-wired infrastructure. Fixed wireless is the operation
of wireless devices or systems in homes and offices, and in particular, equipment connected to the Internet by the use of specialized modems. A fixed wireless network enables users to
establish and maintain a wireless connection throughout or between buildings, without the limitations of wires or cables.
There are two types of wireless networks: peer-to-peer
and access point or base station. A peer-to-peer wireless network
consists of a number of computers, each equipped with a wireless networking interface card. Each computer can communicate directly with all of the other wireless-enabled computers
and equipment (e.g., printers). An access point or base station
wireless network has a computer or receiver that serves as the
point at which the network is accessed. It acts like a hub, which
provides connectivity for the wireless equipment.
Two modes of transmission are used in fixed wireless
systems in buildings: infrared and radio frequency. Infrared
(IR) wireless is the use of technology in devices or systems that
convey data through infrared radiation. Radio frequency (RF)
wireless transmits data through radio wavelengths. Infrared radiation is electromagnetic energy at wavelengths somewhat
longer than those of visible red light. Radio wavelengths are
much longer than infrared wavelengths. The shortest wavelength IR borders visible red in the electromagnetic radiation
spectrum; the longest wavelength IR borders radio waves. Both
infrared and radio wavelengths are invisible to the unaided eye.
IR wireless is used for short- and medium-range communications. Some systems operate in a line-of-sight mode, which
means that there must be a visually unobstructed straight-line
path through space between the transmitter (source) and receiver (destination). Other systems operate in diffuse mode,
where the system can function when the source and destination
are not directly visible to each other. However, IR wireless cannot pass through walls, so a link is not possible between different rooms in a building or between different buildings (unless
they have facing windows). Despite these limitations, most IR
wireless systems offer a level of security comparable to that of
hard-wired systems. It is difficult, for example, to eavesdrop on
a well-engineered, line-of-sight, IR communications link.
IR wireless technology can be used in home entertainment control units; robot control systems; medium-range, lineof-sight communications (e.g., cordless microphones, headsets,
modems, printers, and other peripherals).
RF wireless technology uses radio waves to send and receive information, similar to a garage door opener, baby monitor,
walkie-talkie, or portable phone. It can transmit data through
walls and between nearby buildings. This characteristic offers
flexible linking capability between communication devices.
However, communication on RF wireless is less private; it is
much easier to eavesdrop on a RF communications link in comparison to IR wireless and hard-wired system technologies.
Wi-Fi (derived from the term wireless fidelity) is the popular expression used to describe high-frequency wireless local
area network (WLAN) technology. Wireless hotspots provide
Internet access using wireless network devices installed in public locations. By installing an inexpensive PC card, a laptop
computer can send and receive data at a very high speed, to any
other computer in range. Wi-Fi technology can be set up for use
either free or with a paid subscription in public places such as
airports, hotels, coffee shops, civic plazas, conference centers,
school buildings, and libraries where the user can access e-mail
or the Internet without being directly connected with wiring to
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a local network. It can serve as a LAN in a building that has not
been pre-equipped with cable. Wi-Fi technology can be used at
home where a computer can be connected to the Internet anywhere in the home without being wired. As a result, Wi-Fi is
the pre-eminent technology for building general purpose wireless networks.
Wi-Fi technology can be used for both data and voice
(e.g., telephone) transmission. It is rapidly gaining acceptance in
the business world as an alternative to a wired LAN. However,
unless adequately protected with security safeguards (e.g., firewalls and encryption techniques), Wi-Fi technology can be susceptible to access from the outside by unauthorized users who
simply access the Internet for free or pirate company secrets.
The transmission media chosen for a network is related to
the topology, protocol, and size of the network. In some cases,
a network will use only one type of cable, while other networks
will use a variety of cable types, and others will rely upon wireless technology.
Electromagnetic Interference
Electrical current flow in power lines generates an electromagnetic field that surrounds the electrical conductor. Electrical
equipment, especially large motors, generators, induction
heaters, arc welders, x-ray equipment, and radio frequency, microwave, or radar sources, also produce a powerful electromagnetic field. The ballasts of fluorescent and high-intensity
discharge (HID) fixtures also produce a significant electromagnetic field.
A telecommunication cable placed within an electromagnetic field will have its telecommunication signal affected. This
is known as electromagnetic interference. Because of potential
for electromagnetic interference, voice and data telecommunications cabling should not be run adjacent and parallel to power
(electrical) cabling unless the cables are shielded and
grounded. For low-voltage telecommunication cables, a minimum 5-in (125 mm) distance is needed from any fluorescent
lighting fixture or power line over 2000 volt-amperes (VA) and
up to 24 in from any power line over 5000 VA. In general,
telecommunications cabling is routed separately, or several feet
away from power cabling. For similar reasons, telecommunications cabling must be routed away from electrical equipment.
22.2 STRUCTURED BUILDING
TELECOMMUNICATION SYSTEMS
Wiring and Cabling Standards
Prior to 1991, the manufacturers of electronics equipment controlled the specifications of telecommunications cabling. Endusers were frequently confused by manufacturers’ conflicting
claims concerning transmission performance and were forced
to pay high installation and administration costs for proprietary
CHAPTER 22
systems. The communications industry recognized the need to
define a cost-effective, efficient cabling system that would support the widest possible range of applications and equipment.
The EIA, TIA, and a large consortium of leading telecommunications companies worked cooperatively to create the
American National Standards Institute (ANSI)/TIA/EIA-5681991 Commercial Building Telecommunications Wiring Standard. Additional standards documents covering pathways and
spaces, administration, cables, and connecting hardware were
subsequently released. The ANSI/TIA/EIA-568-1991 was revised in 1995, and is now referred to as ANSI/TIA/EIA-568-A
Commercial Building Telecommunications Cabling Standard.
The goal of these standards is to define structured cabling a
telecommunications cabling system that can support virtually
any voice, imaging, or data application that an end-user chooses.
As the acceptance of standards-compliant structured cabling has grown, the price of installed networking equipment
has dropped and performance has exponentially increased. The
physical layer has evolved into an affordable bandwidth-rich
business resource.
Telecommunication Cabling
and Pathways
Telecommunication cabling is the medium through which voice
and data move from one telecommunication device to another.
Cabling physically carries electrical or optical signals to and
from devices and equipment in a telecommunication system.
Cabling media typically used include UTP and STP copper
wire, coaxial cable, and optical fibers. Wireless technology can
also be used.
A pathway is a passageway, and thus a path, for cable to
travel when interconnecting devices, components, and equipment in a telecommunication system. Pathways are typically a
raceway, a channel, or trough designed to hold wires and cables
(e.g., conduit, cable trough, cellular floor, electrical metallic
tubing, sleeves, slots, underfloor raceways, surface raceways,
lighting fixture raceways, wireways, busways, auxiliary gutters,
and ventilated flexible cableways). Raceways may be metallic
or nonmetallic and may totally or partially enclose the cabling.
Pathways can carry existing cable and that easily allow
additional cabling to be installed to accommodate the addition
of equipment or upgrades in technology. In a building telecommunications system, pathways typically run between the building entrance facilities/equipment rooms, telecommunication
closets, and the work area where telecommunication equipment
and devices are used by building occupants.
A backbone is a generic term used to describe a main
pathway or cabling media that interconnects a number of
telecommunication devices. A backbone is used to connect networks in a building or in separate buildings. Fiber optic cable is
typically used for this type of backbone. Drop cables may be
attached from the backbone to connect individual workstations.
Common types of backbone cabling are provided in Table 22.5.
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BUILDING TELECOMMUNICATION SYSTEMS
TABLE 22.5
COMMON TYPES OF BACKBONE CABLING IN USE.
Cabling Types
Maximum Backbone
Distances
Meters
Feet
Twisted Copper Wire
100 ohm UTP (24 or 22 AWG)
for voice transmission
800
2625
150 ohm STP for data transmission
90
295
Multimode optical fiber (62.5>125 µm)
for voice/data transmission
2000
6560
Single-mode optical fiber (8.3>125 µm)
for voice/data transmission
3000
9840
Optical Fiber Cables
schematic of a structured telecommunications cabling system.
These subsystems are described in the following sections.
Interbuilding Backbone
The interbuilding backbone is the cabling and pathways outside
of the building, including the cables carrying local exchange
carrier (LEC) services (e.g., outside telephone company), Internet service provider services, and private branch exchange
(PBX) telecommunication cable (e.g., private phone network
between buildings at a school campus or business park). Simply, the interbuilding backbone caries telecommunication services to the building.
Building Entrance Facilities
Structured Cabling Systems
A structured cabling system is the cabling, devices, and equipment that integrate the voice, data, video, and electronic management systems of a building (e.g., safety alarms, security
access, energy management and control systems, and so on).
Design and installation of structured cabling systems adheres to
national and international standards.
In commercial buildings, structured telecommunications
cabling systems include seven subsystems. Figure 22.2 is a
The building entrance facility is an entrance to the building for
both public and private network service cables. It includes the cables, connecting hardware, protection devices, and other equipment needed to connect the interbuilding backbone cabling to the
backbone cabling in the building. See Photos 22.2 and 22.3.
PHOTO 22.2 Internet service building entrance. (Used with
permission of ABC)
FIGURE 22.2
cabling system.
A schematic of a structured telecommunications
PHOTO 22.3 Local exchange carrier (LEC) and private branch
exchange (PBX) building entrance. (Used with permission of ABC)
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In buildings with a finished floor area larger than
20 000 ft2 (1870 m2), a secured (locked), dedicated, enclosed
room is recommended for the building entrance. An industry
standard is to allow 1 ft2 (0.1 m2) of 3⁄4-in (20-mm) plywood
wall-mount area for each 200 ft2 (19 m2) area of finished floor
area. The plywood allows mounting capabilities for equipment
and panels. In large buildings, rack-mounted and freestanding
frames may also be required to support entrance equipment
within the build entrance facilities.
Telecommunications Equipment Room
A telecommunications equipment room is a centralized space
for housing main telecommunications equipment. It is a large,
dedicated, centralized room that provides a controlled environment to house equipment, connecting hardware, splice closures, grounding and bonding facilities, and protection
apparatus. Equipment rooms typically accommodate equipment of higher complexity than telecommunications closets
(see below); however, any or all of the functions of a telecommunications closet may be performed in an equipment room
(see patch panels). A telecommunications equipment room
serves a building or multiple buildings in a campus or business
park environment. See Photos 22.4 and 22.5.
The building entrance facilities should be located adjacent to or contained within the equipment room to allow shared
air conditioning, security, fire control, lighting, and limited access. An industry standard is to allow 0.75 ft2 (0.07 m2) of
equipment room floor area for each 100 ft2 (9 m2) of user workstation area, or about 1 to 2 ft2 (0.1 to 0.2 m2) of equipment
room floor area per workstation, with a minimum floor area of
150 ft2 (14 m2). At least two walls should be covered with 8 ft
(2.6 m) high, 3⁄4 in (20 mm) thick, fire-rated plywood to attach
equipment.
A secured (locked), dedicated equipment room is recommended. Doors providing access to an equipment room should be
at least 36 in (900 mm) wide by 8 ft (2.45 m) high. Piping, ductwork, mechanical equipment, or electrical wiring should not enter
the equipment room. The room should not serve as an unrelated
storage room (e.g., for storage of paper and cleaning supplies).
PHOTO 22.4 Telecommunications room and equipment, including
server, router and switches. (Used with permission of ABC)
PHOTO 22.5 Electrical panelboard providing filtered “clean” power
to telecommunications room equipment. Battery-backup provides an
interruptible power supply. Note the fire alarm and manual pull station
nearby. (Used with permission of ABC)
The equipment room should be located away from
sources of electromagnetic interference (e.g., transformers, motors, x-ray equipment, induction heaters, arc welders, radios,
radar systems, and so on). Air conditioning should be provided
(24 hours/day, 365 days/year, at temperatures of 64° to 75°F,
with 30% to 55% relative humidity). General lighting (50 footcandles @ 3 ft above floor) and a minimum of two dedicated
15 A, 120 V ac duplex convenience receptacles on separate circuits should be provided. Additional duplex convenience receptacles should be placed at 6 ft (2 m) intervals around the
perimeter. Emergency power should be considered and supplied.
Telecommunications Closet
A telecommunications closet is a dedicated room on each
floor in a building that houses intermediate voice and data
telecommunications equipment and related cable connections. A large building will have several telecommunications
closets, and more than one on a floor. The telecommunications closet should be located in a space that is central to the
work areas it serves. A telecommunications closet is shown in
Photo 22.6.
Each telecommunications closet serves as a location
where junctions between the backbone pathway and horizontal
pathways are made at one or more patch panels. A patch panel
is a mounted hardware unit containing an assembly of rows of
connecting locations in a communications system, called ports.
A port is receptacle that is a specific place for physically connecting a device or piece of equipment to another. In a network,
a patch panel is located in a telecommunications closet to serve
as a type of switchboard-like device that allows network circuiting arrangements and rearrangements by simply plugging
and unplugging a patch cord. A patch cord is a type of jumper
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BUILDING TELECOMMUNICATION SYSTEMS
PHOTO 22.6 Telecommunications closet. (Used with permission
PHOTO 22.8 Telephone patch panel and cables. (Used with permis-
of ABC)
sion of ABC)
cable that is used to create a connection from one port in a
patch panel to another port. (See Photos 22.7 and 22.8.)
A locked, dedicated telecommunications closet is recommended. The recommended closet size is 10 ft # 12 ft
(3 m # 4 m), about 120 ft2 (11 m2) for each 10 000 ft2 (940 m2)
useable floor area served. More than one telecommunications
closet per floor is required if the distance to a work area exceeds 300 ft (90 m), or if the floor area served exceeds
10 000 ft2 (940 m2).
Two walls in a telecommunications closet should be covered with 8 ft (2.6 m) high, 3⁄4 in (20 mm) thick, fire-rated plywood to attach equipment (e.g., patch panels). Power, lighting,
and air conditioning requirements for a telecommunications
closet are the same as for a telecommunications equipment
room (see previous section). (See Photo 22.9.)
When possible, telecommunications closets should be
stacked vertically above each other on each floor. An industry
standard is to provide at least three 4-in (100 mm) diameter
sleeves (a stub of conduit through the floor) per 50 000 ft2
(4676 m2) of finished floor area served. An equivalent
4 in # 12 in (100 mm # 300 mm) slot may be used in lieu of
three sleeves. If closets are not vertically aligned, then 4 in
(100 mm) diameter horizontal conduit runs are required, with
no more than two 90° bends between pull points. When there are
multiple telecommunications closets on a single floor, it is recommended that these multiple closets be interconnected with at
least one 3-in (75 mm) diameter conduit or an equivalent pathway. To prevent the spread of fire, provisions for a firestop are
required in every opening that penetrates the telecommunications closet compartment (e.g., walls and floors).
Backbone Pathway
Within a building telecommunications system, the backbone
pathway connects the entrance facilities/equipment room to the
telecommunications closets for cabling that interconnects equipment and devices in these spaces. It contains several backbone
PHOTO 22.7 Patch panels and patch cables. (Used with permission
of ABC)
PHOTO 22.9 Wall-mounted telecommunications panels. (Used with
permission of ABC)
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(main) cables that carry the heaviest telecommunications traffic
throughout the building. It is usually a vertical arrangement that
connects floors in a multistory building. However, the same
function may be served by a lateral backbone for horizontal
distribution in a large building with spacious floors.
A building’s backbone pathway consists of the backbone
cables, intermediate and main cross-connects, mechanical terminations, and patch cords used for backbone-to-backbone
cross-connection, connections between floors (risers), and cables between an equipment room and building cable entrance
facilities.
The backbone pathway can hold any type or combination of transmission media, but cabling typically includes
UTP, STP, and optical fiber cable. Backbone cabling distances
are dependent on the type of system, data speed, and the manufacturer’s specifications for the system electronics and the associated components used (e.g., adapters, line drivers, and so
on). All cables in the backbone pathway are typically strung in
a star topology. This configuration allows modifications to be
made without the hassle of having to pull new cables. (See
Photos 22.10, 22.11, and 22.12.)
Horizontal Pathways
PHOTO 22.10 Horizontal backbone cabling in a wire tray. (Used with
PHOTO 22.12 Horizontal backbone cabling entering a firewall. The
permission of ABC)
openings are sealed with an approved firestopping material. (Used with
permission of ABC)
Horizontal pathways connect the backbone cabling entering
the telecommunications closet with the terminal equipment in
the work area (e.g., computers, data terminals, telephones, and
so on). Horizontal pathways can include underfloor ducts embedded in concrete decks or slabs, modular/cellular (raised)
floors, underground trench ducts, and raceways (e.g., conduits,
cable trays, recessed molding). A raised floor system is shown
in Photos 22.13 and 22.14.
The most commonly used horizontal pathway consists of
cable bundles run from the telecommunications closet along
J-hooks or cable trays suspended above a plenum ceiling. Once
a work area is reached, the cabling fans out and individual cable
drops through interior walls, support columns, or chases, eventually terminating at a telecommunications outlet.
The horizontal cabling system extends from the work
area (workstation) outlet to the telecommunications closet and
consists of horizontal cabling, telecommunications outlet, table
terminations, and cross-connections. Types of media used for
horizontal cabling include UTP, STP, and optical cable, each
extending from the telecommunications closet to the work area
at a maximum distance of 294 ft (90 m).
PHOTO 22.11 Bundled horizontal backbone cabling. CAT 3 PBX
telephone cable, CAT 5e data transmission cable, interduct sheathing
containing fiberoptic cable, and two bundled interduct sheathings
containing fiberoptic cable. (From rear to front of photograph). (Used
with permission of ABC)
PHOTO 22.13 Raised floor system (open) containing cabling. (Used
with permission of ABC)
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BUILDING TELECOMMUNICATION SYSTEMS
PHOTO 22.14 Raised floor system (closed). (Used with permission
of ABC)
All cables in horizontal pathways should be strung in a
star topology so cables directly link the telecommunications
closet with each telecommunications outlet. Again, this
arrangement allows alterations to be made without the hassle of
having to pull new cables.
An industry standard is to size horizontal pathways by
providing 1 in2 (645 mm2) of cross-section area for every 100 ft2
(9.3 m2) of workspace area being served. Easy access to the horizontal cabling is desirable. A pull box, splice box or pulling
point is required for any pathway where there are more than two
90° bends, a 180° reverse bend or length more than 100 feet.
PHOTO 22.16 A work area above a raised floor system. (Used with
permission of ABC)
PHOTO 22.17 A workstation. (Used with permission of ABC)
Work Area
The work area is the space containing workstation (terminal)
equipment and components. The workstation components include equipment and devices (e.g., telephones, personal computers, graphic or video terminals, fax machines, modems) and
terminal patch cables (e.g., modular cords, PC adapter cables,
fiber jumpers, and so forth) that connect work area equipment
to the network. Work area wiring is designed to be relatively
simple to interconnect so that modifications and additions can
be easily accomplished. The work area can also be served by a
wireless access point. (See Photos 22.15 through 22.19.)
PHOTO 22.18 A workstation connection with telecommunications
and power outlets. (Used with permission of ABC)
PHOTO 22.15 A wireless access point (station). (Used with permission
of ABC)
A typical telecommunications outlet is made in a
2 in # 4 in (50 mm # 100 mm) electrical box with horizontal
cabling terminating at a connector on the faceplate covering
the box. It is necessary to consider the number and type of devices to be connected when selecting the outlet capabilities and
capacities. Industry practice is to provide a minimum of two
telecommunications outlet/connectors at each work area. At
areas where telecommunications use is anticipated to be heavier than normal (e.g., reception areas, secretarial areas, and
control desk areas), additional outlets will be required. Patch
cables connect work area equipment and devices to a telecommunications outlet. A maximum length of 33 ft (10 m) is typically allowed for work area patch cables.
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that distributes these services to locations throughout the house
in a way similar to how an electrical panelboard distributes and
controls flow of electricity.
A single metal box typically serves as the distribution
center. It is a stand-alone piece of equipment that contains distribution devices. It provides universal access to various networking elements within the home as well as connection to
service providers. The service center must allow the wiring system to be customized periodically as the network evolves to
accommodate future technologies. The distribution center must
be located in a place that is readily accessible to cabling maintenance. Home telecommunication components and wiring are
shown in Photos 22.20 through 22.22.
Universal Multiuse Outlets
PHOTO 22.19 A telecommunications outlet with coded female
connectors. (Used with permission of ABC)
The telecommunications outlets in a room determine the services that are available in that room. Universal multiuse outlets
can be customized to a consumer’s specific needs based on the
services that are desired in each room (e.g., cable, Internet
22.3 ADVANCED WIRING SYSTEMS
FOR HOMES
Advanced Home
Wiring Systems
An advanced home wiring system allows a homeowner to integrate the control and management of the following subsystems:
• Communication subsystem (e.g., intercom, phone,
message recording, fax and e-mail)
• Entertainment subsystem (e.g., whole-house stereo,
VCR, cable, digital and satellite television, and home
theater system)
• Home office subsystem (e.g., computers, printers and
scanners)
• Environmental control/energy management subsystem
(e.g., control of HVAC equipment, water heater, lighting and other appliances)
• Security/property protection subsystem (e.g., video
surveillance with closed circuit TV, control entry gates
and garage doors, control lawn irrigation)
PHOTO 22.20 An advanced home wiring system service center
with security and wireless capabilities. (Used with permission of ABC)
Wiring System Components
An advanced home wiring system is typically consists of three
main components.
Service Center
The service center, sometimes called the central hub or
distribution center, is the central part of the system that accepts
incoming services and distributes services throughout the
home. It is where all external communication services enter the
residence, including cable TV, telephone, digital satellite
transmission, and Internet service. It serves as a central hub
PHOTO 22.21 Home telecommunication wiring. (Used with
permission of ABC)
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BUILDING TELECOMMUNICATION SYSTEMS
video. Even after the wiring system installation is complete,
outlets can be changed to meet the changing needs of the
homeowner.
High-Performance Cabling
PHOTO 22.22 A residential computerized control panel with IPOD
capabilities. (Used with permission of ABC)
access, telephone, and so on). These outlets are designed to
support a full range of communication technologies with a
variety of flexible configurations, including voice, data, and
Several types of high-performance cable are used, including
CAT 5 UTP copper wire and coaxial cable. Wireless transmission technologies can also be used. In the future, fiber optic
cable may eventually become a medium of choice for some
audio/video applications.
Pathways for cabling run between the service center and
the outlets. For new construction, cable is run in concealed
pathways such as ducts and conduits. Provisions should also be
made for conduit for cable pathways to allow for pulling additional wiring in the future. For retrofits of an existing structure,
wiring can be concealed in attics or crawl spaces wherever possible. For exposed retrofit cabling, the cables should be enclosed
in a protective surface-mount raceway.
STUDY QUESTIONS
22-1. Describe the analog and digital transmission formats.
22-2. Sketch the three types of wiring topologies used in a
telecommunications network.
22-3. Identify and describe the types of transmission media
used in a telecommunications network.
22-4. Identify and describe the main subsystems of a structured cabling system for a building telecommunications network.
22-5. Describe UTP and STP wiring.
22-6. Describe the types of coaxial cable.
22-7. Describe the function of a fiber optic system.
22-8. Describe types of wireless communications used in
buildings.
22-9. Describe the following components:
a. Pathway
b. Drop cables
c. Patch panel
d. Patch cord
e. Telecommunications outlet
22-10. How does electrical equipment (e.g., motors, generators, and so on) affect telecommunication signals?
22-11. How does fluorescent and HID lighting affect telecommunication signals?
22-12. Identify and describe the components of an advanced
home wiring system.
Design Exercises
22-13. Make a visit to a residence with an advanced home
wiring system. Make a sketch of the system and identify
chief components of and their locations in the system.
22-14. Make a visit to a commercial building with a telecommunications network. Make a sketch of the telecommunications network and identify chief components and
their locations in the system. Describe the location,
physical size, and function of each component.