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DB > TDMM Chapter 1 - Part 2 > Flashcards

TDMM Chapter 1 - Part 2 Flashcards

1
Q

Name the three types of transmission circuits

A
  • Simplex
  • Half-Duplex
  • Full-Duplex
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2
Q

What is simplex transmission?

A

The transmission of signals in one direction only

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3
Q

What is half-duplex transmission?

A

The transmission of signals in either direction, but in one direction at a time

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4
Q

What is full-duplex transmission?

A

The transmission of signals in both directions at the same time

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5
Q

Why is asynchronous transmission a popular method of telecommunications among microcomputer users?

A

Because of a common standardized interface and protocol between machines

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6
Q

Why is asynchronous transmission less efficient than synchronous transmission?

A

Because it requires the addition of some combination of start and stop bits to the data stream

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7
Q

How is synchronous transmission performed?

A

By synchronizing the data bits in phase or in unison with equally spaced clock signals or pulses

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8
Q

What is used to prevent confusion of the characters in the data stream

A

Clocking pulses

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9
Q

Who are the intended users of basic rate ISDN?

A

Residential and small business users

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10
Q

What is the total information capacity of basic rate ISDN?

A

144 kb/s (line rate = 160 kb/s)

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11
Q

Who are the intended users of primary rate ISDN North America?

A

Large Business Users

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12
Q

What is the total information capacity of primary rate ISDN North America?

A

1.536 Mb/s (line rate = 1.544 Mb/s)

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13
Q

Delay Skew

A

The difference in propagation delay between any pairs within the same cable sheath

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14
Q

What is the total information capacity of primary rate ISDN Europe?

A

1.92 Mb/s (line rate = 2.048 Mb/s)

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15
Q

Dispersion

A

The loss of signal resulting from the scattering of light pulses as they are transmitted through a medium

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16
Q

HDSL requires no repeaters on lines less than __ for 24AWG

A

~3600m (11,811ft)

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17
Q

What has effectively replaced HDSL?

A

SDSL and other xDSL technologies

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18
Q

What is SDSL?

A

A single-pair version of HDSL, transmitting up to DS1 rate signals over a single balanced twisted pair

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19
Q

What is distance limitations for SDSL?

A

~3000m (9842ft)

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20
Q

What does asymmetric describe about ADSL technologies?

A

That they allow more bandwidth downstream (server to client) than they do upstream (client to server)

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21
Q

What down-to-upstream ratio is required for good Internet performance?

A

At least 10:1

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22
Q

What do ADSL modems use to reduce errors caused by impulse noise?

A

Forward Error Correction (FEC)

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23
Q

What does RADSL allow the Access Provider (AP) to adjust?

A

The bandwidth of the DSL link to fit the need of the application and to account for the length and quality of the line

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24
Q

How does RADSL increase the percentage of users served by DSL services?

A

By extending the possible distance from the subscriber to the Access Provider (AP) facility

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25
Q

What are the target ranges of VDSL downstream rates?

A
  • 12.6 to 13.8 Mb/s
  • 25.92 to 27.6 Mb/s
  • 51.84 to 55.2 Mb/s
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26
Q

What are the general ranges of VDSL upstream rates?

A
  • 1.6 to 2.3 Mb/s
  • 19.2 Mb/s
  • Equal to downstream
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27
Q

How much delay is introduced by interleaving?

A

In the order of 40 times the maximum length correctable impulse

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28
Q

What is a baseband analog video signal?

A

A baseband analog video signal is a continuous varying signal whose magnitude and frequency represent the video content. A baseband video signal contains all the necessary information to reproduce a picture, but it does not modulate an RF carrier

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29
Q

Name two types of baseband signalling

A
  • Composite
  • Component
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30
Q

What information is contained in a composite format analog signal?

A

All the components necessary to construct a monochrome or color picture but no audio information

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31
Q

What colors are used to create a color video picture?

A

Red, Green, Blue (RGB)

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32
Q

How does a component video keep the three color components of an image seperate?

A

With three cables

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33
Q

Why is the RGB signal separated from the luminance signal in a component video?

A

To minimize crosstalk and permit higher resolution

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34
Q

How is RGB signaling typically used?

A

For high-end graphic workstations where the need for higher-quality imaging is required

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35
Q

What does an RF carrier represent?

A

TV Channel

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36
Q

Which categories of balanced twisted-pair cabling support baseband composite signaling?

A

Category 3/Class C or higher
(in excess of ~100M (328ft))

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37
Q

Which categories of balanced twisted-pair cabling support RGB composite signaling?

A

Category 3/Class C or higher
(for a minimum of ~100M (328ft) using passive media adapters)

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38
Q

Which categories of balanced twisted-pair cabling support broadband analog CATV signaling?

A

Category 5e/Class D or higher

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39
Q

What are the components of an idealized transmission line?

A

Two conductors separated by a dielectric material uniformly spaced over the line’s length

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40
Q

What was the basis of the earliest functional model of a transmission line?

A

Resistive loss

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41
Q

How can a transmission line be represented?

A

By an electrical circuit containing only passive components that are arranged in a ladder network

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42
Q

Name the four primary transmission line parameters

A
  • Series resistance
  • Series inductance
  • Mutual capacitance
  • Mutual conductance
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43
Q

What is series resistance?

A

The loop resistance of a pair of conductors for an incremental length

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44
Q

What unit of measure is used to express series resistance?

A

Ohms

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45
Q

What is series inductance?

A

The loop inductance of a pair of conductors for an incremental length

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46
Q

What unit of measure is used to express series inductance?

A

Henries (H)

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47
Q

What is mutual capacitance?

A

The capacitance between a pair of conductors for an incremental length

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48
Q

What unit of measure is used to express mutual inductance?

A

Farads (F)

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49
Q

How can the secondary parameters of a transmission line be determined?

A

The conductance between a pair of conductors for an incremental length

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50
Q

What unit of measure is used to express mutual conductance?

A

Siemens (S)

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51
Q

What forms the foundation of EM wave theory?

A

Maxwell’s equations

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52
Q

How can the secondary parameters of a transmission line be determined?

A
  • By calculating the primary parameters
  • By direct measurement
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53
Q

When is maximum power transferred from the source to the load?

A

When the source impedance (Zs) and the terminating impedance (Zt) are equal to the complex conjugate of the transmission line characteristic impedance (Zo)

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54
Q

What term refers to the ratio of output to input power (or voltage) where the terminations are perfectly matched?

A

Attenuation

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55
Q

What term describes signal interference between cable pairs?

A

Crosstalk

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56
Q

How is NVP for balanced twisted-pair cables expressed?

A

As a percentage of the speed of light

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57
Q

What is the range of typical NVP values for 100 ohm balanced twisted-pair cables?

A

.56c to .74c

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58
Q

What term is used to describe the difference in propagation delay between any pairs within the same cable sheath?

A

Delay Skew

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59
Q

What term describes the ratio between the transmitted power and the reflected power?

A

Return Loss

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60
Q

What is the signal-to-noise ratio (SNR)?

A

The ratio between the level of the received signal at the receiver end and the level or transmitted signal

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61
Q

How is attenuation-to-crosstalk ratio (ACR) obtained?

A

By subtracting the attenuation (dB) from near-end crosstalk (NEXT) (dB)

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62
Q

How is ACR normally stated?

A

At a given frequency

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63
Q

What is power sum attenuation-to-crosstalk ratio (PSACR)?

A

A ratio in decibels determined by subtracting the attenuation from PSNEXT loss

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64
Q

What is power sum attenuation-to-alien crosstalk ratio at the near end (PSAACRN)?

A

A ratio in decibels determined by subtracting the attenuation from PSANEXT loss between cables or channels in close proximity

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65
Q

What is power sum attenuation-to-alien crosstalk ratio at the far end (PSAACRF)?

A

A ratio in decibels determined by subtracting the attenuation from the PSAFEXT loss between cables or channels in close proximity

66
Q

How do cabling standards define a channel?

A

All cables, cords and connectors from an equipment connection at one end to the equipment connection at the other end

67
Q

What is the nominal characteristic impedance of balanced-twisted pair cables?

A

100ohms at 100MHz

68
Q

What is the nominal characteristic impedance of balanced twisted-pair cables?

A

100ohms at 100MHz

69
Q

Name the three most important parameters that affect the performance of balanced twisted-pair network cabling

A
  • Insertion Loss
  • PSNEXT Loss
  • Return Loss
70
Q

What is channel insertion loss?

A

The sum of the attenuation of the various components in the test channel, plus all the mismatch losses at cable and connector interfaces, and the increase in attenuation adjusted for temperature

71
Q

What is NEXT loss in a channel?

A

The vector sum of crosstalk induced in the cable, connectors and patch cords

72
Q

What is power sum equal level far-end crosstalk (PSELFEXT)

A

A computation of the unwanted signal coupling from multiple transmitters at the near end into a pair measured at the far end

73
Q

What determines the available channel bandwidth for a specified channel?

A

The range of frequencies that can be successfully transmitted for a given distance

74
Q

What is the dominant noise source for most LAN systems today?

A

NEXT interference between all transmit pairs and a receive pair

75
Q

How much horizontal cabling may be used in a permanent link?

A

Up to ~90m (295ft)

76
Q

True or False
The transmission categories of all components used in the same cabling system must be matched

77
Q

What category/class of balanced twisted pair cable provides the minimum acceptable performance level for network cabling?

A

Category 3/Class C

78
Q

What category/class of balanced twisted-pair cable is recommended as the minimum by most standards?

A

Category 5e/Class D

79
Q

What category/class of balanced twisted-pair cable represents BICSI best practices for network cabling?

A

Category 6/Class E

80
Q

What frequency is supported by Category 3/Class C cable?

81
Q

What frequency is supported by Category 5/Class D cable?

82
Q

What frequency is supported by Category 6/Class E cable?

83
Q

How many 10BASE-T systems can share a binder group?

A

No more than 12

84
Q

Name the three advantages of media conversion to balanced twisted-pair

A
  • It can be a cost effective solution
  • Moves can be simpler to implement
  • Less space in risers or conduits is required
85
Q

Name the three main categories of terminal interfaces

A
  • Impedance-matching devices
  • Signal converters
  • Media filters
86
Q

How are baluns used?

A

To adapt the balanced impedance of twisted-pairs to the unbalanced impedance of coaxial cables

87
Q

Where are baluns required?

A

Wherever a transition is made from twisted-pair to coaxial or from coaxial to twisted-pair

88
Q

What is a signal converter?

A

An electronic device that receives one type of signal and outputs another type of signal

89
Q

Name two advantages of signal converters

A
  • Decrease the risk of transmission and EMI problems
  • Extend the unbalanced signal reach of a DTE
90
Q

What is the purpose of a media filter?

A

To eliminate unwanted frequencies affecting link performance that could radiate from the balanced twisted-pair cable

91
Q

What is a transceiver?

A

A radio frequency device capable of sending and receiving radio frequencies

92
Q

Name the four benefits of combining power and data onto a single cable

A
  • Eliminating the need to provide ac electrical outlets at the same location
  • Faster installation times
  • Detecting loss of power to a device
  • Backup power to network devices
93
Q

What is the maximum power output for Type 1 POE?

94
Q

What is the maximum power output for Type 2 POE?

95
Q

What is the maximum power output for Type 3 POE?

96
Q

What is the maximum power output for Type 4 POE?

97
Q

What is link layer discovery protocol (LLDP)?

A

Type 3 or 4 PSE power classification information exchanged during initial negotiation

98
Q

Name three practical power sourcing equipment (PSE) options for POE

A
  • Endspan devices
  • Midspan devices
  • Local power sources
99
Q

Name the three elements of a simple telecommunications system

A
  • transmitter
  • receiver
  • medium
100
Q

What is the purpose of an optical transmitter?

A

To convert electrical signals to optical signals for transmission over an optical fiber cable

101
Q

What are the four nominal wavelengths of optical fiber transmitters?

A
  • 850nm
  • 1300nm
  • 1310nm
  • 1550nm
102
Q

What term refers to the range of wavelengths over which the total power emitted by a transmitter is distributed?

A

Spectral Width

103
Q

What unit of measure is typically used to specify spectral width?

A

Nanometer (nm)

104
Q

How do wide spectral widths affect the dispersion of light pulses?

A

Wide spectral widths lead to increased dispersion of light pulses as the light pulses propagate through an optical fiber

105
Q

What is the average power of a transmitter?

A

The mean level of power output of a given light source during modulation

106
Q

What is the modulation frequency of a transmitter?

A

The rate at which the transmission changes in intensity

107
Q

Name the three major types of transmitter light sources

A
  • LED
  • VCSEL
  • LD
108
Q

What center wavelength ranges are typical for LEDs?

A
  • 800 to 900 nm
  • 1259 to 1350 nm
109
Q

What is the modulation frequency of most LEDs?

A

Under 200 MHz

110
Q

What is the average launched optical power level of LEDs?

A

-10 to -30 dBm into multimode fiber

111
Q

What is the center wavelength for short wavelength lasers?

112
Q

How does the modulation frequency of short wavelength lasers compare to that of LEDs?

A

It is higher than LEDs (can exceed 1 GHz)

113
Q

What is the average launched optical power level of short wavelength lasers?

A

+1 to -8 decibels per mW (dBm)

114
Q

What are the center wavelengths used for VCSELs?

A
  • 850 nm
  • 1300 nm
115
Q

How does the modulation frequency for VCSELs compare to that of LEDs?

A

It is much higher than LEDs, allowing up to 56GHz

116
Q

What is the average launched power level of VCELs?

A

-1 to -8 decibels per milliwatt into multimode fiber

117
Q

What is the predominate center wavelength for laser diodes (LDs)?

118
Q

How does the spectral width for LDs compare to that of LEDs?

A

Narrow in comparison

119
Q

Whereare typical LD sources used?

A

Almost exclusively in singlemode optical fiber links

120
Q

What is the average launched optical power level of LDs?

A

Common values of +4 to -9 power level decibels per milliwatt into singlemode optical fibers

121
Q

Which type of transmitter is the most expensive: LED, VCSEL or LD?

122
Q

What is the primary type of optical fiber used with LD transmitters?

A

Singlemode

123
Q

Name the three characteristic parameters of optical fiber receivers

A
  • Sensitivity
  • Bit Error Rate (BER)
  • Dynamic Range
124
Q

Define sensitivity in terms of optical fiber receivers

A

The minimum power level an incoming signal must have to achieve an acceptable level of performance

125
Q

What is bit error rate (BER)?

A

The fractional number of errors allowed to occur between the transmitter and receiver

126
Q

What happens to the BER (bite error rate) if the power of the incoming signal falls below the receiver sensitivity?

A

The number of bit errors will increase beyond the maximum BER specified for the receive

127
Q

What is dynamic range?

A

The range of power that a receiver can process at a specified bit error rate (BER)

128
Q

Name the three key factors that are used to determine which optical fiber to use in a given application

A
  • Active equipment
  • Distance
  • Bandwidth (data rate)
129
Q

Which classes of multimode cable are recognized for use in new installations?

A
  • OM3
  • OM4
  • OM5
130
Q

Name the two essential determinants of the end to end bandwidth for an optical fiber system

A
  • Transmitter
  • Optical Fiber
131
Q

What is rise time?

A

The time it takes transmitters to change from a low poweer state (logical 0) to a high power state (logical 1)

132
Q

How does dispersion affect a light pulse?

A

It causes the light pulse to broaden in duration as it travels through the optical fiber

133
Q

What is often used in place of bandwidth to define system capacity in singlemode systems?

A

Maximum Pulse Distortion

134
Q

Name the three effects that are combined to calculate and predict the bandwidth requirements for a multimode system

A
  • Transmitter rise time
  • Optical fiber modal dispersion
  • Chromatic Dispersion
135
Q

What type of dispersion occurs when the wider range of wavelengths in each pulse travels at a wider range of individual speeds?

A

Chromatic Dispersion

136
Q

What is modal dispersion?

A

An event that occurs when a pulse of light, which consists of hundreds of modes in a multimode optical fiber, broadens in time as it travels through the optical fiber

137
Q

What are the two major classifications of optical fiber cable?

A
  • Singlemode
  • Multimode
138
Q

What are the two popular sizes of multimode optical fiber cables?

A

-62.5/125 um
- 50/125 um

139
Q

What are the most common wavelength windows for optical fiber cables?

A
  • 850 nm
  • 1300 nm
  • 1550 nm
140
Q

What is the characteristic core diameter for singlemode optical fiber?

A

Between 8 and 9 um

141
Q

What is the diameter of the cladding on a singlemode optical fiber cable?

142
Q

What is the bandwidth for singlemode optical fiber?

A

Greater than 20 GHz

143
Q

What are the operating wavelengths for singlemode optical fiber?

A
  • 1310 nm
  • 1550 nm
144
Q

What establishes the maximum supportable distance for optical fiber cables?

A

The application standards

145
Q

What establishes maximum channel attenuation?

A

The difference between the minimum transmitter output power coupled into the optical fiber and the receiver sensitivity, less any power penalties established

146
Q

What is the maximum attenuation value for 50/125 um multimode cable at 850 nm?

147
Q

What is the maximum attenuation value for 62.5/125 um multimode cable at 1300 nm?

148
Q

What is the maximum attenuation value for singlemode inside plant cable at 1310 nm?

149
Q

What is the maximum attenuation value for singlemode outside plant cable at 1550 nm?

150
Q

How is optical fiber cable bandwidth validated?

A

Through the manufacturers specification and quality checking of the product specification sheets with the installed components

151
Q

What determines the maximum permissible end to end system attenuation in a given link?

A

The average transmitter power and the receiver sensitivtiy

152
Q

What connector loss value should be used for 0 to 4 connector pairs?

A

The maximum value

153
Q

What connector loss value should be used for 5 or more connector pairs?

A

The typical value

154
Q

What is the recommended loss value for optical fiber cable connectors?

155
Q

What is the average splice loss for fusion splice in multimode cabling?

156
Q

What is the average splice loss for a mechanical splice in singlemode cabling?

157
Q

What is the maximum splice loss for mechanical and fusion splices in multimode cabling?

158
Q

How is the minimum required system loss calculated?

A

By subtracting the receivers dynamic range from the system gain

159
Q

What device can be used to add additional loss to an optical fiber system?

A

Attenuator

160
Q

Name the two standards that have been established for optical fiber carrier transmissions

A
  • Synchronous Optical Network (SONET) - North America
  • Synchronous Digital Hierarchy (SDH) - International

DB (19 decks)

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