This is the Multiple Choice Questions in Chapter 8: The Telephone System from the book Electronic Communication Systems by Roy Blake
Start Practice Exam Test Questions
Choose the letter of the best answer in each questions.
MULTIPLE CHOICE
1. DTMF stands for:
- a. Digital Telephony Multiple Frequency
- b. Dial Tone Master Frequency
- c. Dual-Tone Multifrequency
- d. Digital Trunk Master Frequency
ANS: C
2. PSTN stands for:
- a. Public Switched Telephone Network
- b. Private Switched Telephone Network
- c. Primary Service Telephone Network
- d. Primary Service Telephone Numbers
ANS: A
3. POTS stands for:
- a. Private Office Telephone System
- b. Primary Office Telephone Service
- c. Primary Operational Test System
- d. Plain Old Telephone Service
ANS: D
4. LATA stands for:
- a. Local Access and Transport Area
- b. Local Access Telephone Area
- c. Local Area Telephone Access
- d. Local Area Transport Access
ANS: A
5. A LATA is a:
- a. a local calling area
- b. a type of digital local network
- c. a way of accessing a tandem office
- d. a way of accessing a central office
ANS: A
6. Central offices are connected by:
- a. local loops
- b. trunk lines
- c. both a and b
- d. none of the above
ANS: B
7. Local loops terminate at:
- a. a tandem office
- b. a toll station
- c. a central office
- d. an interexchange office
ANS: C
8. Call blocking:
- a. cannot occur in the public telephone network
- b. occurs on the local loop when there is an electrical power failure
- c. occurs only on long-distance cables
- d. occurs when the central office capacity is exceeded
ANS: D
9. In telephony, POP stands for:
- a. Post Office Protocol
- b. Point Of Presence
- c. Power-On Protocol
- d. none of the above
ANS: B
10. The cable used for local loops is mainly:
- a. twisted-pair copper wire
- b. shielded twisted-pair copper wire
- c. coaxial cable
- d. fiber-optic
ANS: A
11. FITL stands for:
- a. Framing Information for Toll Loops
- b. Fiber In the Toll Loop
- c. Framing In The Loop
- d. Fiber-In-The-Loop
ANS: D
12. Loading coils were used to:
- a. increase the speed of the local loop for digital data
- b. reduce the attenuation of voice signals
- c. reduce crosstalk
- d. provide C-type conditioning to a local loop
ANS: B
13. DC current flows through a telephone:
- a. when it is on hook
- b. when it is off hook
- c. as long as it is attached to a local loop
- d. only when it is ringing
ANS: B
14. The range of DC current that flows through a telephone is:
- a. 20 µA to 80 µA
- b. 200 µA to 800 µA
- c. 2 mA to 8 mA
- d. 20 mA to 80 mA
ANS: D
15. The separation of control functions from signal switching is known as:
- a. step-by-step switching control
- b. crossbar control
- c. common control
- d. ESS
ANS: C
16. The typical voltage across a telephone when on-hook is:
- a. 48 volts DC
- b. 48 volts, 20 hertz AC
- c. 90 volts DC
- d. 90 volts, 20 hertz AC
ANS: A
17. The typical voltage needed to "ring" a telephone is:
- a. 48 volts DC
- b. 48 volts, 20 hertz AC
- c. 90 volts DC
- d. 90 volts, 20 hertz AC
ANS: D
18. The bandwidth of voice-grade signals on a telephone system is restricted in order to:
- a. allow lines to be "conditioned"
- b. prevent "singing"
- c. allow signals to be multiplexed
- d. all of the above
ANS: C
19. VNL stands for:
- a. voltage net loss
- b. volume net loss
- c. via net loss
- d. voice noise level
ANS: C
20. Signal loss is designed into a telephone system to:
- a. eliminate reflections
- b. prevent oscillation
- c. improve signal-to-noise ratio
- d. reduce power consumption
ANS: B
21. The reference noise level for telephony is:
- a. 1 mW
- b. 0 dBm
- c. 1 pW
- d. 0 dBr
ANS: C
22. The number of voice channels in a basic FDM group is:
- a. 6
- b. 12
- c. 24
- d. 60
ANS: B
23. Basic FDM groups can be combined into:
- a. supergroups
- b. mastergroups
- c. jumbogroups
- d. all of the above
ANS: D
24. In telephone system FDM, voice is put on a carrier using:
- a. SSB
- b. DSBSC
- c. PDM
- d. PCM
ANS: A
25. PABX stands for:
- a. Power Amplification Before Transmission
- b. Private Automatic Branch Exchange
- c. Public Automated Branch Exchange
- d. Public Access Branch Exchange
ANS: B
26. SLIC stands for:
- a. Single-Line Interface Circuit
- b. Standard Line Interface Card
- c. Subscriber Line Interface Card
- d. Standard Local Interface Circuit
ANS: C
27. In DS-1, bits are "robbed" in order to:
- a. provide synchronization
- b. carry signaling
- c. cancel echoes
- d. check for errors
ANS: B
28. "Bit-stuffing" is more formally called:
- a. compensation
- b. rectification
- c. justification
- d. frame alignment
ANS: C
29. ISDN stands for:
- a. Integrated Services Digital Network
- b. Information Services Digital Network
- c. Integrated Services Data Network
- d. Information Systems Digital Network
ANS: A
30. Basic ISDN has not been widely adopted because:
- a. it took to long to develop
- b. it is too slow
- c. it has been surpassed by newer technologies
- d. all of the above
ANS: D
31. ADSL stands for:
- a. All-Digital Subscriber Line
- b. Asymmetrical Digital Subscriber Line
- c. Allocated Digital Service Line
- d. Access to Data Services Line
ANS: B
32. Compared to ISDN, internet access using ADSL is typically:
- a. much faster
- b. about the same speed
- c. much more expensive
- d. none of the above
ANS: A
COMPLETION
1. A ____________________ is a local calling area.
ANS: LATA
2. Central offices are connected together by ____________________ lines.
ANS: trunk
3. One central office can be connected to another through a ____________________ office.
ANS: tandem
4. With 7-digit phone numbers, ____________________ thousand telephones can connect to a central office.
ANS: ten
5. Call ____________________ is when it becomes impossible for a subscriber to place a call due to an overload of lines being used.
ANS: blocking
6. New ____________________ switching equipment uses TDM to combine signals.
ANS: digital
7. Most local loops still use ____________________ copper wire.
ANS: twisted-pair
8. As compared to a hierarchical network, a ____________________ network never needs more than one intermediate switch.
ANS: flat
9. ____________________ coils were used to reduce the attenuation of voice frequencies.
ANS: Loading
10. In a twisted-pair telephone cable, the red wire is called ____________________.
ANS: ring
11. In a twisted-pair telephone cable, the green wire is called ____________________.
ANS: tip
12. Of the red and green 'phone wires, the ____________________ wire is positive with respect to the other.
ANS: green
13. A telephone is said to have ____________________ the line when the central office sends it dial tone.
ANS: seized
14. The ____________________ functions are provided by a SLIC.
ANS: BORSCHT
15. A ____________________ coil prevents loss of signal energy within a telephone while allowing full-duplex operation over a single pair of wires.
ANS: hybrid
16. In a crosspoint switch, not all ____________________ can be in use at the same time.
ANS: lines
17. The old carbon transmitters generated a relatively ____________________ signal voltage.
ANS: large
18. The generic term for Touch-Tone® signaling is ____________________.
ANS: DTMF
19. A ____________________ line provides more bandwidth than a standard line.
ANS: conditioned
20. In the telephone system, amplifiers are called ____________________.
ANS: repeaters
21. An echo ____________________ converts a long-distance line from full-duplex to half-duplex operation.
ANS: suppressor
22. ____________________ weighting is an attempt to adjust the noise or signal level to the response of a typical telephone receiver.
ANS: C-message
23. In FDM telephony, the modulation is usually ____________________.
ANS:
SSB
SSBSC
24. In FDM telephony, ____________________ bands separate the channels in a group.
ANS: guard
25. Because of "bit robbing", a channel in a DS-1 frame allows only ____________________ kbps when used to send digital data.
ANS: 56
26. A ____________________ is a group of 12 DS-1 frames with signaling information in the sixth and twelfth frames.
ANS: superframe
27. In DS-1C, ____________________ bits are used to compensate for differences between clock rates.
ANS: stuff
28. Busy and dial tone are referred to as ____________________ signals because they use the same pair of wires as the voice signal.
ANS: in-channel
29. SS7 is the current version of _________________________ signaling.
ANS: common-channel
30. SS7 is a ____________________-switched data network.
ANS: packet
31. In ISDN, the ____________________ channel is used for common-channel signaling.
ANS: D
32. In ISDN, the ____________________ channels are used for voice or data.
ANS: B
33. Terminal equipment especially designed for ISDN is designated ____________________ equipment.
ANS: TE1
34. The A in ADSL stands for ____________________.
ANS: asymmetrical
35. In ADSL, the speed from the network to the subscriber is ____________________ than the speed in the opposite direction.
ANS:
greater
faster
SHORT ANSWER
1. For a certain telephone, the DC loop voltage is 48 V on hook and 8 V off hook. If the loop current is 40 mA, what is the DC resistance of the local loop?
ANS:
1000 ohms
2. For a certain telephone, the DC loop voltage is 48 V on hook and 8 V off hook. If the loop current is 40 mA, what is the DC resistance of the telephone?
ANS:
200 ohms
3. Which two DTMF tones correspond to the digit "1"? (Use the table in the text.)
ANS:
697 Hz and 1209 Hz
4. Calculate the dB of VNL required for a channel with a 3 ms delay.
ANS:
1 dB
5. If a telephone voice signal has a level of 0 dBm, what is its level in dBrn?
ANS:
90 dBrn
6. A telephone test-tone has a level of 80 dBrn at a point where the level is +5dB TLP. If C-weighting produces a 10-dB loss, what would the signal level be in dBrnc0?
ANS:
65 dBrnc TLP
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