* Chapter 1 - Principles of Transmission Flashcards

1
Q

An electrical conductor is

A

any material that can carry an electrical charge from one point to another

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2
Q

The most common electrical conductors in the ITS industry are

A

Copper, Copper Covered Steel, High Strength copper alloys and Aluminum

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3
Q

Copper (Conductor Description)

A

Sets the standard for connectivity of other metals, Annealed copper is used as the reference value (100% conductivity.

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4
Q

Copper-covered (Conductor Description)

A

Also known as copper clad steel, it combines the conductivity of steel copper with the strangth of steel. It is typically used as a conductor for aeiral, self supporting drop wire.

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5
Q

High-Strength (Conductor Description)

A

A mixture of copper and other metals to improve certain copper alloy properties and characteristics of copper. Alloys such as cadmium-chronium copper and zirconium copper offer important weight reductions or greater strength. These factors are especially important in aerospace and other applications.

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6
Q

Aluminum (Conductor Description)

A

Most commonly used in electrical utility distribution lines. It is a malleable ductile light metallic element that has good electrical and thermal conductivity, high reflectivity and resistance to oxidation. It has about 60% conductivity compared with copper and is lighter in weight.

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7
Q

Advantages of Solid Conductors

A

Less Costly - Less complex Terminations - Better Transmission performance at high frequencies - Less Resistance

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8
Q

Advantages of Stranded Conductors

A

More Flexible - Longer flex life - Less susceptible to damage during crimping process

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9
Q

Composite Conductor

A

Term used to describe conductors constructed from nontraditional materials.

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10
Q

Advantages of Composite Conductors

A

Flexible - Light - Inexpensive and easy to produce - Easily embedded into other materials - Low coefficient of expansion

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11
Q

Fluorinated Ethylene Propylene (FEP)

A

Teflon, NEOFLON FEP.

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12
Q

Teflon is a trademark of

A

E.I. du Pont de Nemours & Company.

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13
Q

NEOFLON FEP is a trademark of

A

Daikin America Inc

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14
Q

Halar is a trademark of

A

Solvay Solexis

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15
Q

AWG

A

American Wire Gauge = Generally accepted cable sizing system in North America.

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16
Q

Insulation (also called a dielectric)

A

Used to isolate the flow of current by preventing direct contact between: Conductors, A conductor and its environment.

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17
Q

Insulation (dielectric) is typically made of

A

Plastic materials - applied by a variety of methods. Extruded polymers are generally used as insulation

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18
Q

Cables with a lower dielectric constant and disposition factor have

A

better transmission performance including lower attenuation characteristics and lower capacitance

19
Q

Dielectrics ______ the electromagnetic coupling between conductors by increasing seperation

20
Q

Dielectric Constant

A

The ratio of the capacitance of an insulated conductor to the capacitance of the same conductor uninsulated in the air. Generally a low dielectric constant is desirable

21
Q

Dielectric Strength

A

Measures the maximum voltage that an insulation can withstand without breakdown. A high value for dielectric strength is preferred.

22
Q

Insulated conductors in telecom applications have a typical dielectric strength between _____ and ____V per millimeter.

A

7500 and 30,000 V per millimeter (300 and 1200 V per mil)

23
Q

Dissipation Factor

A

The relative power loss in the insulation due to molecular excitement and subsequent kinetic and thermal energy losses. A low dissipation factor is peferrable

24
Q

Insulation Resistance (IR)

A

The insulation ability to resist the flow of current through it. Typically expressed in megohmkilometer or megohm1,000 feet

25
As cable length increases, the insulation resistance becomes________
smaller
26
The main reason for tight twisting pairs of conductors is to
Minimize crosstalk and noise by decreasing capacitance unbalance and mutual inductance coupling between pairs.
27
A _____ twist between ___ and ___ inches is used for voice and low frequency cables
Counterclockwise, 2in and 6in (.50mm and 150mm)
28
Adjacent pairs are generally designed to have a twist length difference of at at least__________
12.7mm or .5 inches.
29
EMI
Electromagnetic Interference
30
What is EMI?
stray electrical energy radiated from electronic equipment and electronic systems (including cables). EMI can cause distortion or interference to signals in other nearby cables and systems
31
High Temperatures can be routinely encountered in
Exterior Building Walls Ceiling spaces, including plenums Mechanical Rooms
32
Attenuation increases with temperature because of increased:
Conductor Resistance Insulation dielectric constant Dissipation Factor
33
A temperature coefficient of ______ per degree Celsius is not uncommon for some Category 3 cables
1.5%
34
What is a shield?
A metallic covering or envelope enclosing the: - Insulated conductor - Individual group of conductors within a core - Cable core
35
Shields are made of..
Foil or Braided Metal Strands | Usually tinned copper, bare copper, aluminum, or another electrically conductive material
36
When properly terminated, bonded and grounded (earthed) cable shields can
- Reduce the radiated signal from the cable - Reduce the effects of electrical hazards - Minimize the effect of external EMI on the conductors within the shielded cable
37
The effectiveness of a shield depends on factors such as the..
- Type and thickness of the shield - Number and size of the openings in the shield - effectiveness of the bonding connection to the ground
38
What are the steps to convert analog signals to digital?
- Filtering - Sampling - Quantizing/compounding
39
True or False The sampling rate must be at least twice the highest frequency component of the analog signal to faithfully reproduce the analog signal as a digital signal.
True
40
What is a simplex transmission system?
Simplex transmission systems only send signals in one direction
41
What is the signal strength decibel defined as?
Decibel is defined as: dB = 10log(P1/P2) It is the power of signal P1 relative to reference power P2. 3dB indicates a power ratio 2x. So +3dB would double the power.
42
What the three basic components of a transmission system in telephony?
- source of energy (acoustic energy of speech is converted to electrical signal) - medium to carry the energy (a balanced twisted pair is commonly used) - receiving device (transducer in the receiver headset acts a small loudspeaker and converts the electrical signal back to sound energy)
43
True or False A conduit is the best possible shield.
True