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Chapter 2 Flashcards

1
Q

EMC

A

Electromagnetic Compatibility
Ability of a device, equipment, or
system to operate properly in its
intended electromagnetic
environment without introducing
significant electromagnetic
interference (EMI) into
the environment.
TDMM.* Page 2-1

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2
Q

EMI

A

Electromagnetic Interference
The transfer of electromagnetic
energy from one device or
system to another device or
system operating in the same
environment that causes
interference with normal
operation of the devices
or systems.
TDMM.* Page 2-1

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3
Q

Electromagnetic
Emission

A

The phenomenon by which
electromagnetic energy
emanates from a source.
Emissions can be either radiated
or conducted when coupled into
a given disturbed circuit. Such
emissions may be divided into
two categories: intentionally
emitted signals and
unintentional emissions.
TDMM.* Page G-67

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4
Q

Electromagnetic
Immunity

A

The ability of a device,
equipment, or system to perform
without degradation in the
presence of an electromagnetic
disturbance.
TDMM.* Page G-67

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5
Q

EMR

A

Electromagnetic Radiation
Radiation composed of
oscillating electrical and
magnetic fields and propagated
through a medium.
TDMM.* Page 2-2

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6
Q

ESD

A

Electrostatic Discharge
The sudden flow of electricity
between two electrically charged
objects caused by contact.
TDMM.* Page 2-79

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7
Q

Ground Loop

A

Two parallel paths that have
identical conductive
terminations to two separate
grounding (earthing) references.
TDMM.* Page 2-27

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8
Q

RFI

A

Radio Frequency Interference
The degradation of a desired
signal at the receptor end
caused by radio frequency
disturbance within the radio
frequency system which is
usually comprised in the
frequency range that includes
LF, MF, I-IF, and VHF.
TDMM.* Page 2-8

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9
Q

Two devices are using
overlapping operational
frequencies within the
same EM environment.
What is the likely affect on
the potential for EMI in this
environment?

A

The potential for EMI is likely to
increase under these conditions.
TDMM.* Page 2-1

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10
Q

Name 4 mechanisms that can create coupling between two circuits or systems.

A
  1. Conductive coupling
  2. Inductive coupling
  3. Capacitive coupling
  4. Electromagnetic coupling
    TDMM: Page 2-1
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11
Q

What type of coupling may
occur when a common ac
branch circuit is shared
between two devices?

A

Conductive coupling
TDMM: Page 2-1

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12
Q

What causes
inductive coupling?

A

Magnetic fields
TDMM.* Page 2-1

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13
Q

What causes
capacitive coupling?

A

Electric fields
TDMM.* Page 2-1

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14
Q

Name 3 essential elements
of any EMC problem.

A
  1. Source of an EMI or
    electromagnetic energy transfer
  2. Susceptible device or system
    that cannot perform as designed,
    configured, or programmed
    because of the EMI event
  3. Coupling path that promotes the
    disturbance
    TDMM.* Page 2-1
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15
Q

Name 8 examples of EMR.

A
  1. Gamma rays
  2. X-rays
  3. UV light
  4. Visible light
  5. IR radiation
  6. Radar
  7. Microwaves
  8. Radio waves
    TDMM.* Page 2-2
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16
Q

What is the speed of light?

A

300,000 km/s (186,300 mi/s) in a vacuum
TDMM.* Page 2-2

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17
Q

Name the 2 characteristics that are used to distinguish electromagnetic waves.

A
  1. Wavelength (expressed in meters)
  2. Frequency (expressed in hertz)
    TDMM.* Page 2-2
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18
Q

How many frequency
bands are recognized by
the ITU?

A

12
TDMM.* Page 2-2

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19
Q

True or False
Visible light represents the
largest portion of the
electromagnetic spectrum.

A

False. Visible light represents
only a small portion of the
electromagnetic spectrum.
TDMM.* Page 2-3

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20
Q

Name the 3 primary paths
through which conducted
coupling may affect
electronic devices.

A

1.lnput signal lines
2.0utput signal lines
3.Utility or premises electrical
power distribution
TDMM.* Page 2-4

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21
Q

Name the 4 primary
conditions that allow
radiated interference to
enter electronic devices.

A

1 .Proximity to interfering sources
2.Missing or inadequate
gaskets/enclosures
3.Missing or inadequate bonding
and grounding (earthing) system
components
4.Missing or inadequate device or
cable shielding
TDMM.* Page 2-4

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22
Q

True or False
Electrical codes do not
generally provide for EMC.

A

True. Electrical codes do not
generally provide for EMC.
TDMM.* Page 2-4

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23
Q

What is an
electromagnetic field?

A

An area of energy that surrounds
electrical devices
TDMM.* Page 2-6

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24
Q

What type of charge
creates an electric field?

A

Stationary
TDMM.* Page 2-6

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25
What type of charge creates a magnetic field?
Moving (electrical currents) TDMM.* Page 2-6
26
Normally, it is not practical to control external sources of EMI. What methods should the ICT designer use to address this type of EMI instead?
Revert to methods that promote system immunity. TDMM.* Page 2-6
27
What is a reliable and effective technique for mitigating the effects of radio frequency interference on telephone sets?
Deploying shielded or screened structured cabling systems in concerned areas TDMM: Page 2-8
28
Why is it difficult to determine a device's EMC?
Because its value is relative to the environment in which it will operate TDMM.* Page 2-9
29
Name the 2 components of EMC.
1 .Emission 2.Immunity TDMM.* Page 2-9
30
What units of measure are used to describe magnetic fields?
Amperes per meter TDMM.* Page 2-9
31
What frequency spectrum is typically used for measuring conducted
100 kHz to 30 MHz TDMM.* Page 2-9
32
What frequency spectrum is typically used for measuring radiated interference?
30 MHz to 5 GHz TDMM.* Page 2-9
33
How is immunity to radiated emissions
By exposing the device being measured to a specified electromagnetic field and monitoring its performance TDMM.* Page 2-9
34
Name 4 types of radiated interference measurements.
1 .Anechoic chamber 2.TEM cell 3.Reverberating chamber 4.GHz TEM cell TDMM.* Page 2-70
35
Name 3 types of conducted interference measurements.
1 .CM and DM interferences 2.Conducted electromagnetic noise on power supply lines 3.Conducted EMI from equipment TDMM.* Page 2-10
36
What is the acceptance criteria for field intensity for telecommunications equipment and cabling?
3 V/m maximum TDMM.* Page 2-17
37
What major parameters are likely to fail field testing on a trial link if elevated levels of EMI are present?
Crosstalk (such as NEXT and ANEXT) TDMM.* Page 2-11
38
What design factor could cause EMI on a telecommunications system?
Excessive lengths of unshielded cable between rooms of buildings TDMM.* Page 2-12, Table 2.1
39
What 4 design factors could cause EMI on a site's telephone distribution system?
1. Unbalanced cabling 2. Incorrect or missing primary protectors 3. IncompatibIe secondary protectors 4. Incorrect or missing grounds TDMM.* Page 2-14, Table 2.2
40
What is the aim of EMC?
To ensure that equipment items or systems will not interfere with or prevent each other's operation through spurious emission and absorption of EMI TDMM.* Page 2-15
41
What is the focus of EMC?
To control EMI TDMM.* Page 2-75
42
True or False The EMI problem is always a circuit.
True. The EMI problem is always a circuit. TDMM.* Page 2-75
43
True or False EMI is often easy to remedy once the root cause is identified.
True. EMI is often easy to remedy once the root cause is identified. TDMM.* Page 2-75
44
Name 3 common sources of EMI problems.
1 .Conducted and radiated emission sources 2. Transfer of propagation sources 3.Receiving or receptor TDMM.* Pages 2-15 to 2-16
45
Name 2 natural sources of EMI.
1 .Atmospheric electricity 2.Cosmic radiation or geomagnetism disturbances TDMM.* Page 2-16
46
Name 6 man-made sources of EMI.
1.Electrical power 2.Communications electronics 3.Relay communications 4.Tools and machines 5.Ignition systems 6.Industrial and consumer equipment or products (non-motor/engines) TDMM.* Pages 2-16 to 2-17
47
Name 3 methods used to suppress or prevent unwanted signals.
1. Shielding 2. Filtering 3. Bonding and grounding (earthing) of cable shields and equipment TDMM.* Page 2-18
48
Name 3 types of ESD.
1 .Discharge through a spark in the air 2.Radiated effects of ESD 3.Contact discharge TDMM.* Page 2-19
49
How many levels of immunity are used to describe ESD?
4 TDMM.* Page 2-19
50
What voltage level is associated with Level 1 immunity for contact discharge?
2kV TDMM.* Page 2-19, Table 2.3
51
What voltage level is associated with Level 2 immunity for contact discharge?
4 kV TDMM.* Page 2-19, Table 2.3
52
What voltage level is associated with Level 3 immunity for contact discharge?
6 kV TDMM.* Page 2-19, Table 2.3
53
What voltage level is associated with Level 4 immunity for contact discharge?
8 kV TDMM.* Page 2-19, Table 2.3
54
What voltage level is associated with Level 1 immunity for air discharge?
2 kV TDMM.* Page 2-19, Table 2.3
55
What voltage level is associated with Level 2 immunity for air discharge?
4 kV TDMM.* Page 2-19, Table 2.3
56
What voltage level is associated with Level 3 immunity for air discharge?
8 kV TDMM: Page 2-19, Table 2.3
57
What voltage level is associated with Level 4 immunity for air discharge?
15kV TDMM.* Page 2-19, Table 2.3
58
What is the electrostatic discharge susceptibility voltage range for vertical metal oxide semiconductors?
30 to 1800 v TDMM.* Page 2-20, Table 2.4
59
What is the electrostatic discharge susceptibility voltage range for operational amplifiers?
190 to 2500V TDMM.* Page 2-20, Table 2.4
60
What is the electrostatic discharge susceptibility voltage range for resistors?
300 to 3000 V TDMM.* Page 2-20, Table 2.4
61
What can cause a telecommunications cable to store energy and then discharge it as ESD?
Mutual capacitance TDMM.* Page 2-20
62
What is the relationship between the category of a balanced cable and its ability to store energy?
The higher the cable category, the lower its ability to store energy. TDMM.* Page 2-21
63
What is the mutual capacitance range for category 3 cable?
64 to 66 pF/m TDMM: Page 2-27, Table 2.5
64
What is the mutual capacitance range for category 5e cable?
44 to 49 pF/m TDMM.* Page 2-21, Table 2.5
65
What is the mutual capacitance range for category 6 cable?
44 to 46 pF/m TDMM: Page 2-27, Table 2.5
66
What is the mutual capacitance range for category 6A cable?
43 to 45 pF/m TDMM.* Page 2-21, Table 2.5
67
What is the mutual capacitance value for category 8 cable?
1.2 pF/m TDMM.* Page 2-21, Table 2.5
68
Name the 2 types of unwanted signals on a cable in an EMI event.
1 .Common mode (CM) 2.Differential mode (DM) TDMM.* Page 2-24
69
Which type of unwanted signal involves a ground plane?
Common mode (CM) TDMM.* Page 2-24
70
When does a CM signal become evident?
Only when measured against a reference ground TDMM.* Page 2-24
71
How do CM unwanted signals directly affect equipment operation?
By entering the equipment and causing logical errors TDMM.* Page 2-24
72
What is the primary way that DM noise affects equipment?
By corrupting transmitted signals on a balanced circuit TDMM.* Page 2-25
73
What is the relationship between the transmission rate of cabling and interference?
The higher the transmission rate, the higher the effect of the interference. TDMM.* Page 2-26
74
What term describes two parallel paths that have identical conductive terminations to two separate grounding (earthing) references?
Ground loop TDMM.* Page 2-27
75
True or False The earth is always one of the parallel paths between the grounding references in a ground loop.
False. The earth is often, but not always, one of the parallel paths between the grounding references in a ground loop. TDMM.* Page 2-27
76
What is the purpose of electromagnetic shielding?
To reduce or prevent coupling of undesired radiated electromagnetic energy into a given system to enable it to operate properly in its electromagnetic environment TDMM.* Page 2-33
77
Name the 2 approaches to using cable shielding as an EMI mitigation technique.
1 .Low-frequency noise mitigation 2.High-frequency noise mitigation TDMM.* Page 2-33
78
What absorbs the majority of EMI effects at lower frequencies?
Cable twists TDMM.* Page 2-33
79
What part of the cable absorbs the majority of EMI effects at higher frequencies?
The cable shield TDMM.* Page 2-33
80
How does passing through a medium affect the amplitude of an electromagnetic wave?
It decreases exponentially. TDMM.* Page 2-33
81
What parameter best describes the cable shielding response?
Shielding effectiveness TDMM.* Page 2-33
82
What is transfer impedance?
A ratio of the voltage induced on the inside surface of the shield to the current flowing on its outside surface TDMM.* Page 2-34
83
What type of connection is made to ground cable shields?
A 360-degree connection, avoiding breaches in the conductor continuity TDMM.* Page 2-34
84
What type of cable has been the traditional choice for buildings with high levels of ambient EMI?
Shielded cable TDMM.* Page 2-35
85
What device may be used in branch circuits to limit the propagation of electrical surges and associated interference?
Surge protectors TDMM.* Page 2-35
86
How does cable category for balanced twisted-pair cable relate to noise?
A higher category results in a better noise rejection response. TDMM.* Page 2-36
87
What should be used to reduce EMI when signal lines are found close to switchgear?
Localized magnetic barriers TDMM.* Page 2-36
88
Name 5 methods for reducing EMI from fluorescent lighting.
1 .Place a shielding grid over the lamp. 2.Install shielded cable between the lamp and the electrical power switch. 3.Install a metal-enclosed electrical power switch. 4. place a filter between the electrical power switch and the electrical power line. 5.Shield the electrical power line cable. TDMM.* Page 2-37
89
Name 2 means of reducing high levels of noise on power branch circuits.
1 .Line conditioners 2.Surge protectors TDMM.* Page 2-37
90
What is the minimum recommended separation distance between unshielded power lines and non-metal telecommunications pathways?
=610 mm (24 in) TDMM: Page 2-38, Table 2.6
91
What is the minimum recommended separation distance between an electric motor or transformer and telecommunications equipment?
~1220 mm (48 in) TDMM: Page 2-38, Table 2.6
92
What is the recommended minimum separation distance between metallic cabling and a fluorescent lamp?
=127 mm (5 in) TDMM.* Page 2-38, Table 2.7
93
True or False An electric power line EMI filter is mandatory in all active equipment.
True. An electric power line EMI filter is mandatory in all modern electronics (active equipment) for conducted emissions or susceptibility aspects or both. TDMM.* Page 2-39
94
What is the primary function of an isolation transformer for data signals?
To interrupt the CM ground loop at the receiver or transmitter end TDMM.* Page 2-40
95
Define mode conversion.
Transfer of CM voltage to a secondary of the transformer as DM noise TDMM.* Page 2-40
96
Where are isolation transformers commonly used?
In LAN and other digital communications applications TDMM.* Page 2-40
97
Where are isolation transformers commonly used?
In LAN and other digital communications applications TDMM.* Page 2-40
98
What is the desirable minimum CMRR for high quality chokes?
40 dB TDMM.* Page 2-42
99
Name 2 factors that determine the magnitude of electrical powerline influence.
1 .Current that propagates over the power line 2.Physical configuration of the line TDMM.* Page 2-44
100
Name 2 characteristics of telecommunications circuits that determine susceptibility.
1. Amount or presence of shielding 2. Balance of the telecommunications circuit TDMM.* Page 2-47
101
What is the recommended overall longitudinal balance for use at low frequencies?
60 dB or greater TDMM.* Page 2-48
102

MJ Class (23 decks)

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