Chapter 17: The Telephone Circuit – Tomasi Review

(Last Updated On: March 17, 2020)

Chapter 17: The Telephone Circuit

This is the summary notes of the important terms and concepts in Chapter 17 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.


CHAPTER 17

THE TELEPHONE CIRCUIT


Items

Definitions

Terms

1

It comprised of two or more facilities, interconnected in
tandem, to provide a transmission path between a source and a destination.

Telephone Circuit

2

The information transferred in a telephone circuit

Message

3

The circuit used in transferring information in a telephone
circuit.

Message Circuit

4

The network bandwidth for a standard voice-band message
channel.

4 kHz

5

Unused frequency bands located between information signals.

Guard Bands

6

Effective channel bandwidth for a voice-band message signal.

300 Hz to 3000 Hz

7

The only facility required by all voice-band circuits, as it
is the means by which subscriber locations are connected to the local
telephone company

Local Subscriber Loop

8

The primary cause of attenuation and phase distortion on a
telephone circuit.

Two components found on local loops:
Loading Coils
Bridge Taps

9

The largest cable used in a local loop, usually 3600 pair of
copper wire placed underground or in conduit.

Feeder Cable (F1)

10

A cross-connect point used to distribute the larger feeder
cable into smaller distribution cables.

Serving Area Interface

11

A smaller version of a feeder cable containing less wire
pairs.

Distribution Cable

12

A device that serves as the demarcation point between local
telephone company responsibility and subscriber responsibility for telephone
service.

Subscriber or Standard
Network Interface (SNI)

13

The final length of cable pair that terminates at the SNI.

Drop Wire

14

That portion of the local loop that is strung between poles.

Aerial

15

The location where individual cable pairs within a
distribution cable are separated and extended to the subscriber’s location on
a drop wire.

Distribution Cable and Drop Wire Cross Connect
Point

16

Adding inductors periodically in series with the wire.

Loading

17

The inductor in loading technique.

Loading Coil

18

An irregularity frequently found in cables serving subscriber
location.

Bridge Tap

19

A loss that allows signals to split and propagation down more
than one wire introduced by bridge taps.

Bridging Loss

20

Weighting network introduced by AT & T to accomplish equal
magnitude of noise signals.

C-Message Weighting

21

The most annoying frequency to human (i.e. the best frequency
response).

1000 Hz

22

The basic yardstick used for making power measurements in
communications.

Decibel (dB)

23

The optimum level of a test tone on a channel at some point in
a communications system. It is used for voice circuits.

Transmission Level Point
(TLP)

24

The ratio in dB of the power of a signal at that point to the
power the same signal would be at 0 dBm transmission level point.

Transmission Level
(TL)

25

The reference for TLP.

0 dBm

26

A parameter equivalent to TLP except it is used as a reference
for data transmission.

Data Level Pint
(DLP)

27

dBm reference to a zero transmission level point.

dBmO

28

dB reference value for noise reading.

reference noise (rn)

29

dB level of noise with respect to reference noise (- 90 dBm).

dBrn

30

Similar to dBrn except it is the dB value of noise with
respect to reference noise using C-message weighting

dBrnc

31

Noise readings taken with a filter that has a flat frequency
response from 30 Hz to 3 kHz

dBrn 3 kHz Flat

32

The amount of noise in dBrnc corrected to a 0 TLP

dBrncO

33

Identify when transitions occur in the data and whether that
transition is from a 1 to a 0 or vice versa.

Three-Bit Code

34

Transmission parameters which include terminal impedance, in
band and out of band signal power, test signal power and ground isolation.

Interface Parameters

35

Transmission parameters which includes noise measurements,
frequency distortion, phase distortion, amplitude distortion and non linear
distortion.

Facility Parameters

36

The difference in circuit gain experienced at a particular
frequency with respect to the circuit gain of a reference frequency.
Another names attenuation distortion:
·        
Frequency
Response,
·        
Differential
Gain
·        
1004-Hz
Deviation

Attenuation
Distortion

37

An indirect method of evaluating the phase delay
characteristics of a circuit.

Envelope Delay Distortion

38

It satisfies the minimum line conditioning requirements

Basic Voice-Band Channel

39

Another name for basic voice-band.

Basic 3002 Channel

40

Specifies the maximum limits for attenuation distortion and
envelope delay distortion.
Classifications of C-type:
·        
C1
·        
C2
·        
C3
·        
C4
·        
C5

C-type Conditioning

41

Classification of C-type conditioning pertains to two point
and multi point circuits.

C1 and C2

42

C-type conditioning used for access lines and trunk circuits
associated with private switched networks.

C3

43

C-type conditioning pertains to two point and multi point
circuits with a maximum of four stations

C4

44

C-type conditioning pertains to two point circuits only

C5

45

A relatively low-capacity switching machine where the
subscribers are generally limited to stations within the same building or
building complex.

Private Branch Exchange
(PBX)

46

The frequency response of a transmission medium referenced to
1004 Hz test tone.

Attenuation Distortion

47

A requirement for error free data transmission.

Linear Phase vs. Frequency

48

The difference in phase shifts with respect to frequency that
signals experience as they propagate through a transmission medium.

Delay Distortion

49

The time delay encountered by a signal as it propagates from
source to a destination.

Propagation Time

50

The delay measured in angular units.

Phase Delay

51

The actual time required for a particular frequency to
propagate from a source to a destination through a communications channel.

Absolute Phase Delay

52

The time required to propagate a change in an AM envelope
through a transmission medium.

Envelope Delay

53

The phase difference at the different carrier frequencies.

Envelope Delay Distortion

54

It sets the minimum requirements for signal to noise ratio and
nonlinear distortion.

D-Type Line Conditioning

55

The data transmission rate when D type conditioning is
mandatory.

9600 bps

56

Telephone industry standard test tone frequency

1004 Hz

57

Measurement that determine the average weighted rms noise
power.

C-message Noise Measurement

58

A communications term that indicates the presence of a signal
power comparable to the power of an actual message transmission.

Loaded

59

Characterized by high amplitude peaks of short duration having
an approximate flat frequency spectrum

Impulse Noise

60

A sudden, random change in the gain of a circuit resulting in
a temporary change in the signal level.

Gain Hit

61

A decrease in circuit gain of more than 12 dB lasting longer
than 4 ms.

Dropout

62

A sudden, random changes in the phase of a signal.

Phase Hits (Slips)

63

A form of incidental phase modulation – a continuous,
uncontrolled variation in the zero crossings of a signal.

Phase Jitter

64

The presence of one or more continuous, unwanted tones within
a message channel.

Single Frequency Interference

65

Unwanted tones within a message channel.

Spurious Tones

66

The frequency of the signal changes during transmission.

Frequency Shift

67

It occurs in coherent SSBSC systems when the received carrier
is not reinserted with the exact phase relationship to the received signal as
the transmit carrier possessed.

Phase Intercept Distortion

68

It occurs in coherent SSBSC systems when the received carrier
is not reinserted with the exact phase relationship to the received signal as
the transmit carrier possessed.

Phase Intercept Distortion

69

A four wire circuit an interface.

Hybrid Set

70

Another name for hybrid set.

Terminating Set

71

Any disturbance created in a communications channel by signals
in other communications channels.

Crosstalk

72

Annoying and objectionable because the listener senses a real
or fancied loss of privacy

Intelligible crosstalk

73

It does not violate privacy, although it can still be
annoying.

Unintelligible crosstalk

74

A direct result of nonlinear amplification in analog
communications system.

Nonlinear Crosstalk

75

Electromagnetic coupling between two or more physically
isolated transmission media.

Coupling Crosstalk

76

Interference caused by inadequate control of the transfer
characteristics or transmittance of networks.

Transmittance Crosstalk

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