Week 2 Chapter 1 Part 1 - Pages 1-1 to 1-40 Flashcards
Principles of Transmission
Echoes of voice occur at all times. In telephony, delays greater than _____ milliseconds (ms) are perceptible if they are of sufficient strength.
a. 50
b. 40
c. 30
d. 20
a. 50
p 1-22
For an echo to be experienced, there must be enough delay for it to be distinguishable from the original source of the sound. In telephony, delays greater than 50 ms are perceptible if they are of sufficient strength.
Which one of the following statements about loading coils is false?
a. They cut off frequencies above the voice range
b. They compensate for the capacitance of a cable pair
c. They block analog high fidelity signals
d. They improve speech transmission quality
e. They have no effect on data transmission
e. They have no effect on data transmission
p 1-25
Although loading coils improve speech, they adversely affect data transmission. While loading improves the loss versus frequency characteristics, it causes severe delay problems.
Composite conductors have poor analog transmission characteristics, especially above 4000 Hz.
a. True
b. False
a. True
p 1-5
Disadvantages of composite conductors include the following:
• Poor analog transmission characteristics, including high attenuation, especially above 4000 Hz
• Poor digital transmission characteristics
• Easily damaged unless encased in a rigid material
• Inconsistent quality
The characteristics impedance of telephone cable pairs is approximately _____ for 26 AWG cables.
a. 900 ohms
b. 600 ohms
c. 300 ohms
a. 900 ohms
p 1-24
The characteristic impedance of telephone cable pairs is approximately 600 ohms for 22 AWG cables and 900 ohms for 26 AWG cables.
An analog signal is in the form of a wave that uses continuous variations in time (e.g., voltage amplitude or frequency variations) to transmit information.
a. True
b. False
a. True
p 1-17
There is an inverse relationship between insulation resistance and cable length.
a. True
b. False
a. True
p 1-8
There is an inverse relationship between insulation resistance and cable length (i.e., as the cable length increases, the insulation resistance becomes smaller).
When compared to copper, high-strength conductors such as cadmium-chromium copper and zirconium copper have a conductivity rating of approximately:
a. 90%
b. 85%
c. 75%
d. 60%
e. 50%
b. 85%
p 1-3
Note, aluminum has about 60% conductivity compared with copper
Drain wires are sometimes applied in place of a shield to provide an easier means for grounding (earthing) the shield and to ensure shield continuity for metallic shields.
a. True
b. False
b. False
p 1-16
Key word is “in addition”, not “in place”.
Drain wires are sometimes applied in addition to a shield to provide an easier means for grounding (earthing) the shield and to ensure shield continuity for metallic foil shields. A drain wire running the length of the cable next to the shield provides ample grounding (earthing).
“The insulation’s ability to resist the flow of current through it” is the definition of:
a. Insulation resistance
b. Dissipation factor
c. Dielectric strength
d. Dielectric constant
a. Insulation resistance
p 1-8
The insulation’s ability to resist the flow of current through it. For inside conductors, IR is typically expressed in megohm•km or megohm•1000 ft.
Which one of the following types of insulation has the smallest dielectric constant?
a. PVC
b. XL polyolefin
c. ECTFE
d. PE
e. FEP
e. FEP
p 1-7 Table 1.3
Historically, polyvinyl chloride insulated conductors were commonly used for outside plant cables.
a. True
b. False
b. False
p 1-6
Historically, telecommunications cable conductors were insulated with PVC and PE. PVC-insulated conductors were commonly used for inside plant cables, and PE-insulated conductors were commonly used for OSP cables.
Which one of the following types of cable shields get a shield effectiveness rating of “poor” for fatigue life?
a. Foil / foil + braid
b. Single-layer braid
c. Multiple-layer braid
d. Flexible conduit
e. Solid conduit
e. Solid conduit
p 1-15 Table 1.5
Which one of the following types of cable shield get a shield effectiveness rating of poor for tensile strength?
a. Flexible conduit
b. Foil/foil + braid
c. Solid conduit
d. Single-layer braid
e. Multiple-layer braid
b. Foil/foil + braid
p 1-15 See table 1.5
Stranded conductors are less costly than solid conductors.
a. True
b. False
b. False
p 1-4
Advantages of solid conductors include the following:
• Less costly
• Less complex termination systems
• Better transmission performance at high frequencies
• Less resistance
Advantages of stranded conductors include the following:
• More flexible
• Longer flex life
• Less susceptible to damage during crimp termination processes
Cables with a lower dielectric constant and dissipation factor have better transmission performance.
a. True
b. False
a. True
p 1-6
Cables with a lower dielectric constant and dissipation factor have better transmission performance, including lower attenuation characteristics and lower capacitance.
The electrical performance of balanced twisted-pair cables is inversely related to the insulation’s dielectric constant and dissipation factor
