CNSST 3.2: Telephony, Cellular and Facsimile

1. The range of DC current that flows through a telephone is

Ans. 20mA to 80mA

2. The typical voltage needed to “ring” a telephone is:

Ans. 90 volts, 20 hertz AC

3. Central offices are connected by:

Ans. trunk lines

4. Call blocking:

Ans. occurs when the central office capacity is exceeded

5. The cable used for local loops is mainly:

Ans. twisted-pair copper wire

6. Loading coils were used to:

Ans. reduce the attenuation of voice signals

7. Signal loss is designed into a telephone system to:

Ans. prevent oscillation

8. The reference noise level for telephony is:

Ans. 1 pW

9. The number of voice channels in a basic FDM group is:

Ans. 12

10. Minimum quality circuit available using the PTN.

Ans. basic voice channel *

11. In telephone system FDM, voice is put on a carrier using:

Ans. SSB

12. In DS-1, bits are “robbed” in order to:

Ans. carry signaling

13. “Bit-stuffing” is more formally called:

Ans. Justification

14. Compared to ISDN, internet access using ADSL is typically:

Ans. much faster

15. The simplest and most straightforward form of telephone service is called:

Ans. Plain and Old Telephone Service (POTS)

16. The modern Touch-tone telephone is called ______

Ans. 2500-type telephone set

17. The feedback signals that helps prevent the speaker from talking too loudly

Ans. Sidetone

18. Aside from the tip and ring used in local loops the third wire when used is

called _____

Ans. sleeve

19. In RJ-11, the RJ stands for

Ans. Registered Jack

20. It is a combination of passive components that are used to regulate the

amplitude frequency response of the voice signals.

Ans. Equalizer circuit

21. It is a special balanced transformer used to convert a two-wire circuit to a

four-wire circuit and vice-versa

Ans. Hybrid network

22. It is the exchange of signaling messages between switching machines.

Ans. Interoffice signaling

23. Category of signaling message that indicates a request for service, going

off-hook or ringing in the destination telephone.

Ans. Alerting

24. Signals that provide call status information, such as busy or ringing signals

Ans. Supervising

25. Signals that provide information in the form of announcements such as a

number changed to another number, a number no longer in service, and so on

Ans. Controlling

26. Signals that provide the routing information, such as calling and called

numbers

Ans. Addressing

27. It is an audible signal comprised of two frequencies: 350 Hz and 440 Hz

Ans. Dial tone

28. It is a method originally used to transfer digits in the telephone to…..the

local switch

Ans. Dial pulsing

29. This refers to ability of individuals to retain their existing telephone

numbers and the same quality of service when switching to a new location and

service provider.

Ans. local number portability *

30. Systems that are simplex wireless communications systems designed to

….subscribers of awaiting messages

Ans. Paging

31. Early paging system uses what modulation technique

Ans. FM

32. Modern paging system uses what modulation technique

Ans. FSK and PSK

33. These are unused sections of cables that are connected in shunt working

cables….., such as local loop. They are used for party lines.

Ans. Bridge tap

34. It is a parameter equivalent to TLP except that it is used as a reference for

a transmission

Ans. ….. Level Point

35. Weighting technique that assumes a perfect receiver only, therefore its

weighting curve corresponds to the frequency response of the ear only

Ans. …ophometric noise weighting

36. It is the difference in circuit gain experienced at a particular frequency

with respect to the circuit gain of a reference frequency

Ans. Attenuation distortion

37. It is simply the frequency response of a transmission medium referenced

1004-Hz test tone

Ans. Attenuation distortion, Differential gain or 1004-Hz deviation

38. It is an indirect method of evaluating the phase delay characteristics of a

circuit.

Ans. Envelop Delay Distortion

39. The process used to improve a basic telephone channel is called ______.

Ans. Line conditioning

40. Special type of line conditioning that specifies the maximum limit for

attenuation distortion and envelope delay distortion

Ans. C-line conditioning

41. The time delay measured in angular units, such as degrees or radians is

called _____.

Ans. Phase delay

42. The difference between the absolute delays of all frequencies.

Ans. Phase distortion

43. It is the time required to propagate a change in an AM envelope through a

transmission medium

Ans. Envelope delay

44. At the receiver, the phase difference at the different carrier frequencies is

called _____.

Ans. Envelope Delay Distortion

45. The reference frequency of a typical voice-band circuit is typically around

_____.

Ans. 1800 Hz

46. A special type of line conditioning that sets the minimum requirements for

signal-to-noise ratio a nonlinear distortion

Ans. D-type line conditioning

47. It is a communications term that indicates the presence of a signal power

comparable to the power of an actual message transmission

Ans. Loaded

48. It is a sudden, random change in the gain of the circuit resulting in a

temporary change in the signal level

Ans. Gain hits

49. It is the decrease in gain of more than 12 dB lasting longer than 4 ms and a

characteristics of temporary open circuit conditions and are generally caused by

deep fades on radio facilities or by switching delays

Ans. Dropouts

50. It is the sudden, random changes in the phase of the signal. They are

classified as temporary variations in the phase of the signal lasting longer than 4

ms.

Ans. Phase hits

51. It is a form of incidental phase modulation – a continuous uncontrolled

variation in the zero crossings of a signal.

Ans. Phase Jitter

52. Phase jitter occurs at what frequency?

Ans. 300 Hz or lower

53. It is used to convert two-wire circuits to four-wire circuits which is

similar to hybrid coil found in standard telephone sets.

Ans. Hybrid Circuits

54. The talker hears a returned portion of the signal as an echo, what is the

round trip time of delay for an echo to quite annoying?

Ans. 45 msec

55. It eliminates the echo by electrically subtracting it from the original

signal rather than disabling the amplifier in the return circuit.

Ans. Echo cancellers

56. A typical echo suppressor suppresses the returned echo by how much?

Ans. 60 dB

57. A type of cross talk which is a direct result of nonlinear amplification in

analog communications system

Ans. Nonlinear crosstalk

58. In telephony, functions that identify and connect subscribers to a suitable

transmission path

Ans. Switching functions

59. Circuits that are designed and configured for their use only and often

referred to as private circuits or dedicated circuits.

Ans. Leased circuits

60. The operator of the instrument

Ans. Subscriber

61. It is similar to the local loop except that it used to interconnect two

telephone offices.

Ans. Trunk circuits

62. In a telephone channel, _____ is used if the total via net loss of a given

trunk circuit exceeds approximately 2.5 dB.

Ans. echo suppressor *

63. It is a central location where subscribers are interconnected, either

temporarily or on a permanent basis.

Ans. Exchanges

64. The number of dedicated lines used to interconnect 100 parties is

Ans. 4950 lines

65. A switchboard with four digits can accommodate how many telephone numbers

Ans. 10,000

66. The most versatile and popular crossbar switch was ______.

Ans. #5XB

67. The first computer-controlled central office switching system used in PSTN

Ans. No. 1 ESS

68. It is a programmable matrix that allows circuits to be connected to one

another.

Ans. Circuit switch

69. A telephone call completed within a single local exchange is called _______.

Ans. Intraoffice call or Intraswitch call

70. The trunk circuits that are terminated in tandem switches are called ______.

Ans. Tandem trunks or Intermediated trunks

71. When subscriber initiates a long distance call, the local exchange connects

the caller to the toll office through a facility called _____,

Ans. Toll-connecting trunk or Inter-office toll trunk

72. The telephone switching plan that allows a certain degree of route selection

when establishing a phone call

Ans. Switching hierarchy

73. It is simply a path between two subscribers and is comprised of one or more

switches, two local loops or possibly one or more trunk circuits.

Ans. Route

74. A call that cannot be completed because the necessary trunk circuits or

switching paths are not available.

Ans. Blocking

75. Class of switching office which is the local exchange where the subscriber

loops terminated and received dial tone.

Ans. Class 5 End office

76. The class of switching office that provides service to small groups of class

4 offices within a small area of state

Ans. Class 3 Primary center

77. The highest ranking office in the DDD network in terms of size of the

geographical area served and the trunk options available

Ans. Class 1 Regional center

78. It defines the procedures and protocols necessary to exchange information

over the PSTN using a separate digital signaling network to provide wireless and

wireline telephone call setup, routing and control.

Ans. Common Channel Signaling System no. 7 or SS7 or C7

79. A telephone service that uses a common 800 area code regardless of the

location of the destination

Ans. Wide Area Telephone Service (WATS)

80. A mandate that requires all telephone companies to support the porting of

telephone number.

Ans. Local Number Portability

81. It allows customers to change to a different service and still keep the same

phone number

Ans. Porting

82. In SS7, signaling points, codes that are carried in signaling messages

exchanged between signaling points to identify the source and destination of each

message

Ans. Point codes

83. _____ are local telephone switches equipped with SS7-compatible software and

terminating signal links.

Ans. Service Switching Points (SSP)

84. It provides functionality of communicating with the voice switch by creating

the packets or signal units necessary for transmission over the SS7 network.

Ans. Service Switching Points (SSP)

85. 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

86. 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

87. Calculate the dB of VNL required for a channel with a 3 ms delay.

Ans. 1 dB

88. If a telephone voice signal has a level of 0 dBm, what is its level in dBrn?

Ans. 90 dBrn

89. 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

90. AMPS uses the _____-MHz band.

Ans. 800

91. The number of ERP classes in AMPS is _____.

Ans. three

92. A cell phone permanently installed in a car would be ERP class _______.

Ans. I (one)

93. The maximum ERP of class III cell phones is _______.

Ans. 600 mW

94. A portable, handheld cell phone would be ERP class _____.

Ans. III (three)

95. A MAC is a mobile ________ code.

Ans. attenuation

96. A mobile switching center is also call an _________.

Ans. MTSO

97. Telephone call traffic is measured in _______.

Ans. erlangs

98. Traffic model used in telephone system that is based on the assumption, that

calls not immediately satisfied at the first attempt are held in the system until

it is satisfied?

Ans. Erlang C *

99. The reduction in cell size to increase traffic is called cell _______.

Ans. splitting

100. A _____ site is a very small unit that can mount on a streetlight pole.

Ans. microcell

101. Very small cells called ______ are used for reliable indoor reception.

Ans. picocells

102. Compared with AMPS, digital cellular phones require _____ bandwidth.

Ans. less

103. What is the speed of Cellular Data Packet Data (CDPD)

Ans. 17.2 or 19.2

104. In analog CMTS, the interfering signal strength must remain approximately less than

_____ percent of the desired signal strength.

Ans. 2

105. SCM identifies the _______________.

Ans. maximum power level of a cellphone

106. The SID is used by a cell phone to

Ans. recognize that it is “roaming”

107. The CMAC is used to

Ans. set the transmit power of the cell phone

108. In an AMPS system, voice is sent using _____.

Ans. FM

109. In an AMPS system, control-channel signals are sent using _____.

Ans. FSK

110. The ERP of typical handheld AMPS cell phone is

Ans. less than 600 mW

111. The combination of the mobile cell phone and the cell site radio are called the

Ans. air interface

112. Phone traffic is measured in

Ans. erlangs

113. One way to increase the capacity of a cell phone is

Ans. increase the number of cells

114. Base stations transmitter output power of Improved Mobile Telephone Services (IMTS)

Ans. 100-W to 200-W range

115. An area divided into hexagonal shapes that fit together to form a pattern is called

______.

Ans. Cell

116. Macrocells have base stations transmit power between __________.

Ans. 1W to 6W

117. Microcells have base stations transmit power between __________.

Ans. 0.1W to 0.6W

118. A geographic cellular radio coverage area containing three of more group of cells

Ans. Cluster

119. Determine the number of channels per cluster and the total number of channel

capacity of a cellular telephone area comprised of 10 clusters with 7 cells in each

cluster and 10 channels in each cell

Ans. 70 channels per cluster, 700 total channels

120. What is the typical cluster size?

Ans. 3, 7 and 12

121. It is when the area of a cell, or independent component coverage areas of a

cellular system, is further divided, thus creating more cell areas.

Ans. Cell splitting

122. The point when the cell reaches maximum capacity occurs when the number of

subscribers wishing to place a call at any given time equals the number of channels

in the cell.

Ans. Maximum traffic load

123. Determine the channel capacity of a cellular telephone area comprised of seven

macrocell with 10 channels per cell

Ans. 70 channels per area

124. Determine the channel capacity if 7 macrocells with 10 channels per cell is split

into 4 minicells.

Ans. 280 channels per area

125. Decreasing co-channel interference while increasing capacity by using directional

antenna is called _____.

Ans. Sectoring

126. A technique that divides the group of channels into smaller groupings or segments

of mutually exclusive frequencies; cell sites, which are within the reuse distance is

assigned their own segment of the channel group

Ans. Segmentation

127. It is a means of avoiding full-cell splitting where the entire area would otherwise

need to be segmented into smaller cells.

Ans. Dualization

128. Provides a centralized administration and maintenance point for the entire network

and interfaces with the public telephone network through the telephone wireline voice

trunks and data links.

Ans. Mobile Telephone Switching Office (MTSO)

129. It is when a mobile unit moves from one cell to another from one company’s service

area to another company’s service area.

Ans. Roaming

130. The transfer of a mobile unit from one base station’s control to another base

station’s control

Ans. Handoff or Handover

131. An open standard that allows PCs, peripherals, cordless telephones, and other

consumer electronic devices to communicate and interoperate with one another without

the complexity and expense associated with installing new wires?

Ans. Shared Wireless Access Protocol (SWAP)

132. A connection is momentarily broken during the cell-to-cell transfer is called

Ans. Hard handoff

133. A flawless cell-to-cell transfer is called ______.

Ans. Soft handoff

134. Soft handoff normally takes _____ of time delay

Ans. 200 ms

135. In IS-41 standard, it is a process where the mobile unit notifies a serving MTSO of

its presence and location through a base station controller

Ans. Autonomous registration

136. It is a digital telephone exchange located in the MTSO that is the heart of a

telephone system

Ans. Electronic switching center

137. Component of a cellular telephone network that manages each of the radio channels

at each site

Ans. Cell-site controllers or Base station controllers

138. The actual voice channel where mobile users communicate directly with other mobile

or wireline subscriber through the base station

Ans. User channel

139. A channel used for transferring control and diagnostic information between mobile

users and a central cellular telephone switch through the base stations.

Ans. Control channel

140. What modulation technique is used by Advanced Mobile Phone System (AMPS)

Ans. Narrow band FM (NBFM)

141. What is the frequency deviation of AMPS?

Ans. 12 kHz

142. Transmission from mobile stations to the base stations is called _____.

Ans. Reverse link or Uplink

143. Determine the transmit and receive carrier frequencies for AMPS channel 3 and

channel 991.

Ans. 870.09 MHz and 869.04 MHz

144. It is a 34-bit binary code that represents the 10-digit telephone number.

Ans. Mobile Identification Number (MIN)

145. A 32-bit binary code permanently assigned to each of the mobile unit.

Ans. Electronic Serial Number (ESN)

146. Supervisory Audio Tones (SAT) have frequencies

Ans. 5970 Hz, 6000 Hz, and 6030 Hz

147. The bit length of System Identification (SID)

Ans. 15

148. The bit length of Station Class Mark (SCM)

Ans. 4

149. The bit length of Digital Color Code (DCC)

Ans. 2

150. It is a database in the PCS network that stores information about the user,

including home subscription information and what supplementary services the user is

subscribed to.

Ans. Home Location Register (HLR)

151. A database in the PCS network that stores information about subscribers in a

particular MISO serving area.

Ans. Visitor Location Register (VLR)

152. Determine the transmit power for a CDMA mobile unit that is receiving a signal from

the base station at 100 dBm.

Ans. Pt = -76 dB – Pr; Pt =-76 dB – 100; Pt = 24 dBm

153. The North American PCS band is

Ans. 1.9 GHz

154. PCS cells are typically _______ than AMPS cells.

Ans. Smaller

155. IS-136 PCS is usually just called _______.

Ans. TDMA PCS

156. GSM is a _____ system.

Ans. TDMA

157. IS-95 PCS uses ______ technology.

Ans. CDMA

158. Current PCS systems are called ____-generation systems.

Ans. Second

159. Types of Class 4 toll center which provides human operators for both outward and

inward calling service.

Ans. Class 4C

160. The ERP of class II mobile phone used in GSM system.

Ans. 1.6

161. The ESS assigned at the factory of cellular mobile phone, consists of how many

bits?

Ans. 32

162. The speech coding rate for GSM cellular mobile is _______.

Ans. 13 kbps

163. What modulation technique is used by the European Cordless Telephone?

Ans. GFSK

164. Compared to AMPS, PCS cells are _______ in size.

Ans. Smaller

165. The spread-spectrum technique used in IS-95 is ________.

Ans. CDMA (direct sequence)

166. The spread-spectrum technique used in GSM is ________.

Ans. frequency hopping

167. Unlike AMPS, CDMA such as IS-95 allows for a _______ handoff.

Ans. Soft

168. The orthogonal PN sequences used in CDMA are called a ______ code.

Ans. Walsh

169. ______ diversity is inherent in any spread-spectrum system.

Ans. Frequency

170. RF channels S/N ratios _____ than zero is typical in CDMA systems.

Ans. Less

171. CDMA uses a ______-rate vocoder.

Ans. Variable

172. A phone user typically talks less than ________ of the time during a conversation.

Ans. 50%

173. How does GSM achieve frequency diversity?

Ans. It uses limited frequency hopping.

174. Why was PCS assigned to 1.9 GHz instead of the 800-MHz band used for AMPS?

Ans. The 800 MHz band was already overcrowded.

175. The “forward” PCS channel is

Ans. from base to the mobile

176. CDMA technology was invented by

Ans. Qualcomm

177. In GSM, voice channels are called

Ans. traffic channels

178. In CDMA

Ans. all frequencies are used in all cells

179. CDMA uses a set of PN sequences that are _______.

Ans. Orthogonal

180. If a 28.8 kbps modem is being used over a cell phone, how many words of text would

be lost during a 100-msec handoff interruption assuming 10 bits per letter and 5

letters per word?

Ans. 57.6

181. A certain cell site contains 200 cell phones. The probability that cell phone is

being used is 15%. What is the traffic in erlangs?

Ans. 30

182. WISPs offer access to the internet at speed up to _____ Mbps.

Ans. 11 *

183. The data signaling channel in a cellular system that handles the administrative

overhead is known as

Ans. Paging channel

184. The data rate of information transfer of mobile devices using “Bluetooth”

Ans. 1 Mbps

185. The access method used in 3G mobile telephony.

Ans. WCDMA

186. A 3G wireless system promise to increase its network capacity by how much percent

as compared to lower generation wireless system.

Ans. 70

187. In CMTS, the frequency separation between forward and reverse channel is

Ans. 45 MHz

188. The period for a single time slot in the GSM-TDMA slot is ______ µsec.

Ans. 577 *

189. The ratio of the separation distance between two co-channel cells and the cell

radius is known as

Ans. co-channel interference reduction

190. Bluetooth Standard

Ans. IEEE 802.15

191. Bluetooth maximum distance

Ans. 10 m

192. Bluetooth is operating at the ISM frequency range of

Ans. 2.402 – 2.480 GHz *

193. Bluetooth uses

Ans. frequency hopping

194. What is the other name of the IEEE 802.16 standard for broadband wireless

Ans. WiMAX

ACRONYMS

AMPS Advanced Mobile Phone Service

MSC Mobile Switching Center

BSC Base Station Controller

MTSO Mobile Telephone Switching Office

CDPD Cellular Digital Packet Data

NAM Number Assignment Module

CMAC Control Mobile Attenuation Code

PCS Personal Communication Systems

DCC Digital Color Code

PN Pseudo random Noise

EDGE Enhanced Data Rates for Global Evolution

RCC Radio Common Carrier

ERP Effective Radiated Power

SAT Supervisory Audio Tone

ESN Electronic Serial Number

SCM Station Class Mark

ESN Electronic Serial Number

SID System Identification Number

GPRS General Packet Radio Service

SIM Subscriber ID

IMSI International Mobile Subscriber Identification

UPT Universal Personal Telecommunications

IMT International Mobile Telecommunications

UWT Universal Wireless Telecommunications

MIN Mobile Identification Number

WCDMA Wide CDMA

MSC Mobile Switching Center

WISP Wireless Internet Service Provider