Week 29 Chapter 13 Part 3 - Pages 13-70 to 13-108

Question 1

A properly designed overhead paging system will provide an SPL for the voice page that is at least ___ dB, but no more than ___ dB above the ambient noise level

a. 3, 6
b. 6, 6
c. 3, 20
d. 6, 20

Answer 1

d. 6, 20

p 13-84:
If the 6 dB level is not followed, the voice pages:
• May be lost in the ambient noise of the room.
• Will be unintelligible.
If the 20 dB ambient noise level is not followed, the paging will be far too loud in areas closest to the loudspeakers and horns.

Question 2

The ___ is the preferred pattern for loudspeaker distribution because it provides the most uniform coverage.

a. Hexagonal
b. Square

Answer 2

a. Hexagonal

p 13.85

Question 3

In areas with less than ___ dB noise level, the distance between ceiling loudspeakers in a row should be approximately ___ times the ceiling height.

a. 40, 1.5
b. 30, 2
c. 70, 2
d. 50, 1.5
e. 80, 2

Answer 3

c. 70, 2

p 13-86

In areas with less than 70 dB noise level, the distance between ceiling loudspeakers in a row should be approximately twice the ceiling height.

In areas with a noise level greater than 70 dB, the distance between loudspeakers should be decreased.

Question 4

For appropriate sound coverage, wall-mounted loudspeakers should be mounted ___ ft to ___ ft above the floor.

a. 7, 9
b. 8, 12
c. 8, 10
d. 9, 12

Answer 4

b. 8, 12

p 13-86

For appropriate sound coverage, wall-mounted loudspeakers should be mounted ≈2.4 m (8 ft) to ≈3.7 m (12 ft) above the floor. Wall-mounted loudspeakers should not be directed toward each other.

Question 5

For heavy traffic hallways, use ceiling-mounted loudspeakers placed along the center of the hallway ___ ft intervals whenever possible. Place the first loudspeaker ___ ft from the end of the hall and work toward the other end.

a. 8, 8
b. 8, 20
c. 9, 10
d. 9, 20

Answer 5

a. 8, 8

p 13-87

For heavy traffic hallways, use ceiling-mounted loudspeakers placed along the center of the hallway ≈2.4 m (8 ft) intervals whenever possible. Place the first loudspeaker ≈2.4 m (8 ft) from the end of the hall and work toward the other end.

Place a ceiling loudspeaker at hall junctions. In a normal traffic hallway, place loudspeakers at intervals equal to twice the ceiling height.

Question 6

Where ceiling loudspeakers cannot be used, use wall-mounted bidirectional loudspeakers placed at intervals of ___ ft on alternating sides of the hallway. Place the first bidirectional loudspeaker ___ ft from the end of the hall and work toward the other end.

a. 8, 8
b. 8, 20
c. 9, 10
d. 9, 20

Answer 6

b. 8, 20

p 13-87

Where ceiling loudspeakers cannot be used, use wall-mounted bidirectional loudspeakers placed at intervals of ≈8 m (26 ft) on alternating sides of the hallway. Place the first bidirectional loudspeaker ≈6.1 m (20 ft) from the end of the hall and work toward the other end.

Question 7

Horn loudspeakers have a directional projection pattern and are appropriate for use in environments with more than ___ dB of noise.

a. 40
b. 30
c. 70
d. 50
e. 80

Answer 7

c. 70

p 13-87

The loudspeakers may be installed indoors or outdoors or where larger areas must be covered by each loudspeaker. Horns commonly have a higher power rating than ceiling-mounted loudspeakers.

Question 8

In ambient noise levels above ___ dB, coded tones or strobe lights may provide an alternative to standard paging.

a. 80
b. 90
c. 100
d. 110
e. 120

Answer 8

c. 100

p 13-87

In ambient noise levels above 100 dB, coded tones or strobe lights may provide an alternative to standard paging. Many paging controls can activate these devices.

Question 9

A 70 V line can be run ___ times farther than a 25 V line for the same loss.

a. 6
b. 8
c. 10
d. 12

Answer 9

b. 8

p 13-89

A 70 V line can be run eight times farther than a 25 V line for the same loss.

Question 10

Voltage step-down transformers are used at each loudspeaker to convert the 25 V or 70 V signal to a much lower voltage. These transformers are called ___
transformers.

a. Voltage-matching
b. Load-matching
c. Loudspeaker-matching
d. Impedance-matching

Answer 10

d. Impedance-matching

p 13-90

These transformers provide various taps that allow the power to each loudspeaker to be individually adjusted during installation. The tap values may range from
1/8 W to 20 W for most paging applications, up to 200 W for some loudspeakers.

Question 11

Which of the following statement is false about the central amplifier power rating should be based on:

a. The AV source requirements
b. The total sum of the tap wattages of each impedance-matching transformer on each loudspeaker.
c. The total sum of the power lost in the loudspeaker distribution cabling.
d. Power reserved for future growth.
e. Add an additional 25 percent to this number so that the amplifier will normally be operating at about 75 percent of its rated output.

Answer 11

a. The AV source requirements

p 13-91

Question 12

To have a masking system acceptable to those working in the space, the NC should not be higher than ___.

a. 25
b. 35
c. 45
d. 55

Answer 12

b. 35

p 13-92

To have a masking system acceptable to those working in the space, the NC should not be higher than 35. A sound level meter capable of measuring octave band sound levels should be used. For new spaces, the NC can be predicted but should be field verified.

Question 13

The video conferencing camera FOV should NOT be valued higher than ___ degrees or it would be subject to significant optical distortion.

a. 45 degrees
b. 50 degrees
c. 65 degrees
d. 70 degrees

Answer 13

c. 65 degrees

p 13-72

Anything valued higher than 65 degrees FOV is subject to significant optical distortions (e.g., curvature at the image edges eventually extending throughout the image as the FOV gets bigger).

The ratio of optical zoom (e.g., 8:1, 10:1, or 17:1), combined with the FOV number will give the usable range of the camera views

Question 14

Most cameras used in videoconferencing systems use ___ bit processing.

a. 8
b. 10
c. 16
d. 24

Answer 14

b. 10

p 13-73

Most cameras used in videoconferencing systems use 10-bit processing. A 10-bit system has a bright-to-dark range of 1024:1 for all numerical values. A 10-bit system
would limit the potential performance of the camera to resolve about a 1000:1 difference from brightest to darkest elements in a given image.

Question 15

The typical camera used for videoconferencing operates extremely well at ___ lux measured at the subject.

a. 423
b. 526
c. 629
d. 753

Answer 15

d. 753

p 13-75

The typical camera used for videoconferencing operates extremely well at 753 lux (70 fc) measured at the subject. Figure 13.36 shows a typical videoconference light setup.

Question 16

A codec is a small, but critical piece in a videoconferencing system. Which statement is false about a codec:

a. Takes the analog audio and video signals and converts them into digits.
b. Processes the derived digits to reduce the amount of data.
c. Delivers data at a guaranteed rate, reducing the need for buffering.
d. Allows the transmission of the data to a different location over a network.
e. Decompresses the data.
f. Assigns the data to the audio or video decoder, which turns it back into analog signals for listening and viewing.

Answer 16

c. Delivers data at a guaranteed rate, reducing the need for buffering.

p 13-76

A codec is a small, but critical piece, in a videoconferencing system. A codec:
• Takes the analog audio and video signals and converts them into digits.
• Processes the derived digits to reduce the amount of data.
• Allows the transmission of the data to a different location over a network.
• Decompresses the data.
• Assigns the data to the audio or video decoder, which turns it back into analog signals for listening and viewing.

Question 17

___ consists of two user channels of 64 Kb each delivered over a single copper pair similar to a regular telephone line and was originally intended to supplant POTS.

a. BRI
b. PRI

Answer 17

a. BRI

p 13-77

BRI consists of two user channels of 64 Kb each delivered over a single copper pair similar to a regular telephone line and was originally intended to supplant POTS.

PRI contains either 24 or 32 channels of 64-Kb service and is delivered over two pairs of copper wire.

Question 18

Typically, up to ___ BRI circuits are linked together to provide 512 kb/s connectivity.

a. 2
b. 4
c. 6
d. 8

Answer 18

b. 4

p 13-77

Multiple channels of BRI are often collected together and operate as a single higher speed connection in a process called inverse multiplexing. Typically, up to four BRI circuits are linked together to provide 512 kb/s connectivity.

Question 19

Systems requiring only a few loudspeakers are typically better served with a constant ___ design

a. Current
b. Voltage

Answer 19

b. Voltage

p 13-83

Systems requiring more than a few loudspeakers are typically better served with a constant voltage design, which provides a voltage of up to 140 V (i.e., typically 25, 70, or 100), eliminating the need to calculate and balance loads.

Question 20

Masking amplifiers should have ___ V outputs.

a. 25
b. 70

Answer 20

b. 70

p 13-93

Amplifiers should have 70 V outputs. Since a masking system should never be turned off, the amplifiers should be of high quality.

Question 21

The required masking tuning equipment in the United States is an ANSI class ___, ___ octave spectrum analyzer and a high-quality flat response microphone.

a. 1, 1/2
b. 2, 1/2
c. 1, 1/3
d. 1, 1/4

Answer 21

c. 1, 1/3

p 13-94

Question 22

Which articulation index range is considered normal for speech privacy

a. 0.33-0.44
b. 0.20-0.32
c. 0.05-0.19
d. 0.00-0.04

Answer 22

c. 0.05-0.19

p 13-95 Table 13.8

Normal privacy is typically the best that the ICT distribution designer can expect from a properly designed sound masking system in an open office.

Normal privacy means that while occupants are aware of conversations around them, they cannot discern the subject unless they concentrate on them.

Question 23

Multiple ISDN basic rate interface (BRI) channels are often grouped together in a process called _____ in order to operate as a single high speed connection for videoconferencing systems.

a. Channel clustering
b. Link aggregation
c. Circuit bonding
d. Inverse multiplexing

Answer 23

d. Inverse multiplexing

p 13-77

Multiple channels of BRI are often collected together and operate as a single higher speed connection in a process called inverse multiplexing. Typically, up to four BRI circuits are linked together to provide 512 kb/s connectivity.

Question 24

In a cable television distribution system, the subscriber drop is connected to the distribution system at the:

a. Junction
b. Splitter
c. Headend
d. Tap

Answer 24

d. Tap

p 13-100

Subscriber drop—The taps, cable, and telecommunications outlet/connector where the users connect their TV sets or other video devices. The subscriber drop is connected to the distribution system at the tap.

Question 25

Lighting is important for a videoconferencing system since the usual dynamic range for such systems is ___, which is significantly lower than the 1000:1 value for a typical camera.

a. 250:1
b. 200:1
c. 150:1
d. 100:1

Answer 25

b. 200:1

p 13-76

Wide differences in light level—The typical camera has a dynamic range of about 1000:1 from brightest to darkest in a given scene. The usual dynamic range of a videoconference system is around 200:1.

Question 26

Constant _____ centrally amplified paging systems are more common in smaller installations.

a. Balance
b. Load
c. Voltage
d. Current

Answer 26

d. Current

p 13-83

The constant current systems are more common in smaller installations and require more consideration in design because the loudspeakers need to be balanced, based on load rating, typically 4 or 8 ohms.

Question 27

Coaxial cable with a solid copper center conductor and copper braid _____ broadband applications.

a. Is recommended for
b. Should not be used in

Answer 27

b. Should not be used in

p 13-101

Coaxial cable with a solid copper center conductor and copper braid should not be used in broadband applications. This type of coaxial cable is not intended for broadband because it does not effectively shield against ingressing or egressing signals.

Question 28

You are designing a four story retail mall and multiple sound systems within it. Which system should you design to support general music programming within common retail areas?

a. Distributed paging
b. Life safety
c. Sound masking
d. Sound reinforcement and playback

Answer 28

d. Sound reinforcement and playback

Question 29

A space has all hard surfaces including architecture and furnishings. The audio programming produced from the distributed sound system has become unintelligible. Which of the following will NOT mitigate the problem?

a. Add tapestries to the walls.
b. Provide additional speakers at lower output.
c. Increase the volume to the existing speakers.
d. Reduce the distance of the existing speakers to the listener.

Answer 29

c. Increase the volume to the existing speakers.

Question 30

One 15 W horn mounted ≈5 m (16.5 ft) above the floor with a SPL ambient noise of 80 dB angled at 60-degrees will cover how much space?

a. 372 m2 (4000 ft2)
b. 232 m2 (2500 ft2)
c. 112 m2 (1200 ft2)

Answer 30

b. 232m2 (2500ft2)

p 13-87 Table 13.7

Question 31

Within a CATV distribution system, home run design is typically only used in ___ installations.

a. Small
b. Large

Answer 31

a. Small

p 13-102

A home run design is typically only used in small installations.