Telephony Quiz 3

Front 1

transmission of information from one or more sources to one or moredestinations over the same medium

Back 1

Multiplexing

Front 2

conversion of standard logic levels to a formmore suitable for transmission (e.g. digital waveform).

Back 2

Digital Line Encoding

Front 3

transmission of binary data involves transmission of a singlenonzero voltage level.

Back 3

Unipolar transmission

Front 4

transmission of binary data involves transmission of two nonzerovoltage levels

Back 4

Bipolar transmission

Front 5

Two types of duty cycle

Back 5

Nonreturn to Zero (NRZ) and Return to Zero (RZ).

Front 6

a binary pulse is maintained for the entire bit time.

Back 6

NRZ

Front 7

active time of the binary pulse is less than 100% of the bit time.

Back 7

RZ

Front 8

This condition occurs when a long string of 1s (or 0s) causes the receiver to lose its amplitude reference.This would result to misinterpretation of binary data (i.e. 1s may be interpreted as 0s because of the noise margin.

Back 8

DC Wandering in NRZ

Front 9

The minimum bandwidth required to propagate a line-encoded digital signal is_____ to the highest fundamental frequency associated with the signal.

Back 9

equal

Front 10

it is based on the fastest transition in the bitsequence.

Back 10

highest fundamental frequency

Front 11

is easily maintained if there are sufficient transitions in thedata waveform.

Back 11

Synchronization

Front 12

line-encoding have no built-in errordetectionmechanism

Back 12

UPNRZ, BPNRZ, UPRZ and BPRZ

Front 13

With BPRZ-AMI encoding, an error in any bit causes a ___________ or the reception of two or more consecutive logic 1s with the same polarity.

Back 13

bipolar violation (BPV)

Front 14

This ensures that sufficient transitions occur in the data stream (aka onesdensity) by substituting a logic 1 when there are several succeeding logic 0s. Typically applied to T1 system.

Back 14

Binary Eight Zero Substitution (B8ZS)

Front 15

this method ensures that sufficient transitions occur in the datastream when there are successive zeros. Typically applied to T2 system.

Back 15

Binary Six Zero Substitution (B6ZS)

Front 16

this method ensures that sufficient transitions occurin the data stream when there are successive zeros. Typically applied to T3 system

Back 16

Binary Three Zero Substitution (B3ZS)

Front 17

It is a popular type of line encoding that produces a strong timing component forclock recovery and does not cause DC wandering.

Back 17

Digital Biphase

Front 18

is sometimes called the Manchester code.It has no built-in error detection mechanism.It has an average DC voltage of 0V assuming an equal probability of 1s and 0s

Back 18

Digital biphase

Front 19

transmissions from multiple sources occur on the same facilities butnot on the same time. predominantly used for digital signals.

Back 19

Time-Division Multiplexing (TDM)

Front 20

• The fundamental building block for most TDM systems begins with a __________

Back 20

DS-0channel (digital signal level 0).

Front 21

is a communications system that uses digital pulse ratherthan analog signals to encode information

Back 21

digital carrier system

Front 22

___________ is recognized as the NorthAmerican Digital Multiplexing Standard since 1963 and is recognized by ITU-Tas ____________.

Back 22

T1 Digital Carrier, Recommendation G.733.

Front 23

In T1 DC, ____ voice-band channels with ideal bandwidth of ____ Hz arePCM-encoded and multiplexed for transmission over a single metallic wirepair or fiber transmission line.

Back 23

24, 4000

Front 24

D-type (digital) channel banks perform these functions in the PCM-TDM system:(a) ________, (b) ________ and (c) _________ of the 24 voice-band channels.

Back 24

sampling, encoding, multiplexing

Front 25

This was used by early T1 carrier systems. This utilized companding and u = 10.

Back 25

D1 Channel Bank

Front 26

each TDM frame contains 24 channels with one framing bit added at thestart of the frame.

Back 26

D1 Channel Bank

Front 27

In D2 and D3 channel banks, every group of 12 TDM frames is called a __________. (also known as D4 Framing.)

Back 27

superframe (SF)

Front 28

signaling bit was only inserted every 6 frames.

Back 28

D2 and D3 Channel Banks

Front 29

Signaling bit is inserted using ________

Back 29

robbed-bit signaling

Front 30

Types of digital channel banks thatuses extended superframe (ESF)

Back 30

D5

Front 31

For D5 Framing Bits: Only the framing bits found in frames (a) __ , __ , __ , __ , __ , __ are used for framingsynchronization. The framing synchronization sequence is (b) ______.

Back 31

(a) 4, 8, 12, 16, 20 and 24
(b) 001011

Front 32

For D5 Framing Bits:Framing bits found in frames __, __, __, __, __, __ are used for CRC-6 (cyclicredundancy checking), an error detection code.

Back 32

1, 5, 9, 13, 17 and 21

Front 33

For D5 Framing Bits:The 12 Remaining framing bits act as a management channel called _______. These bits occur at 2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 22 and 23.

Back 33

facilities data link (FDL)

Front 34

Frame Durations:
TDM Frame duration (D1 with 8 bits): (a) ____

SF duration (D2 and D3): (b) ____

ESF duration (D5): (c) _____

Back 34

(a) 125 microsecond / frame

(b) 1.5 ms / SF

(c) 3 ms / ESF

Front 35

_____________ distribute the channels in a standard T1 system to severalusers, allowing several subscribers to share one T1 line.

Back 35

Fractional T1 systems

Front 36

Fractional T1 systems most commonly used bit rates: (two)

Back 36

(1) 384 kbps (6 channels or ¼ T1)

(2) 768 kbps (12 channels or ½ T1)*

Front 37

______ is used to combine the transmissions from differentsubscribers and acts as the interface to the digital carrier network.

Back 37

CSU/DSU(Channel service unit/Data service unit)

Front 38

Upgrading from one line type to the next higher requires a separate device called ______

Back 38

Muldem

*M12 Muldem -> From DS-1 to DS-2

* M23 Muldem -> From DS-2 to DS-3

Front 39

Digital signals are routed using ________

Back 39

digital crossconnects (DSX).

*DSX are convenient place to make patchable interconnects and to perform routinemaintenance and troubleshooting.

Front 40

In Europe, a different version of T carrier lines is used, called _______

Back 40

E-lines

Front 41

A basic frame in E1 system is divided into (a) __ equal time slots and multiplexedusing PCM-TDM system. Time slot 0 is used for (b) _________. Time slot 16 is used for (c) ______.

Back 41

(a) 32

(b) frame alignment and alarm

(c) common signaling channel (CSC)

• Remaining time slots for voice signals.

Front 42

One multiframe contains ____ CCITT TDM frames.

Back 42

16

Front 43

________ exploits the natural breaks in transmission bydynamically allocating time slots on a demand basis.

Back 43

statistical TDM.

Front 44

transmissions from multiple sources occur on the same transmissionmedium but are allocated over different frequency bands.

Back 44

Frequency-Division Multiplexing (FDM)

*FDM is an analog multiplexing scheme.

Front 45

transmissions from multiple sources occur on the same transmissionmedium but are transmitted at different wavelengths.

Back 45

Wavelength-Division Multiplexing (WDM)

*Used in optical communications

*Offers higher bandwidth because of optical fibers

* Accomplished by modulating injection laser diodes that are transmittinghighly concentrated light waves at different wavelengths

Front 46

An optical fiber is a strand of (a) ______ or _____ which consists of a (b) ____, ____, _____

Back 46

(a) Silica glass or plastic

(b) core, cladding, protective layer

Front 47

Wavelength spectrum used is in the region of ______ or ______ .

Back 47

1300 or 1500 nm

Front 48

Around ___ optical channels may be multiplexed over a single opticalcable.

Back 48

100

Front 49

is a multiplexing system similar to conventional TDM except that it wasdeveloped to be used for optical fibers.

Back 49

Synchronous Optical Network (SONET)

*Its fundamental building block is an OC-1 (optical carrier level 1) or an STS-1(synchronous transport signal level 1).

Front 50

SONET uses ___________ multiplexing format.

Back 50

byte-interleaved

Front 51

_______ is the fiber-optic system standard all over the world (except North America).

Back 51

Synchronous Digital Hierarchy (SDH)