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IS 3413 > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

What is a physical circuit?

A
  • the actual wire used to connect two devices.

- the physical media that carry the message we transmit.

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2
Q

What is a logical circuit?

A
  • the transmission characteristics of the connection.

- T1 connection, refers to hw fast data can be sent trhough the connection

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3
Q

What is a modem?

A
  • used to send digital data over an analog telephone circuit.
  • translates computer’s digital data into analog data that can be transmitted through the voice communication circuits.
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4
Q

What is a codec?

A

-translates analog voice data into digital form for transmission over digital computer circuits.

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5
Q

Why is digital transmission better?

A
  • produces fewer errors and errors are easier to detect and correct
  • permits higher max transmission rates.
  • more efficient
  • more secure, easier to encrypt
  • integrating voice, video and data on same circuit is simpler.
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6
Q

What is a symbol?

A

-patters of electricity, light or radio wave that will be used to represent a 0 and a 1.

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7
Q

What is a symbol rate?

A

-How many symbols are sent over the circuit per second.

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8
Q

What is circuit configuration?

A

-the basic physical layout of the circuit.

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9
Q

What is a point-to-point circuit?

A
  • goes from one computer to another computer.

- dedicated circuits.

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10
Q

What is a multipoint circuit?

A
  • manyy computers are connected on the same circuit.

- each computer must share the circuit with the others.

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11
Q

What is simplex transmission?

A

-one-way transmission such as radios and TVs

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12
Q

What is half-duplex transmission?

A
  • two-way transmission but you can only transmit in only one direction at a time.
  • walkie-talkie.
  • use of control signals to determine which will send and receive data.
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13
Q

What is turnaround time?

A
  • the amount of time half-duplex communication takes to switch between sending and receiving.
  • also called retrain time.
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14
Q

What is full-duplex?

A

-you can transmit in both directions simultaneously with no turnaround time.

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15
Q

What is multiplexing?

A
  • break one high-speed physical communication circuit into several lower-speed logical circuits so that many devices can simultaneously use it but still think they have their own separate circuits.
  • done in multiples of four
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16
Q

What is the benefit of multiplexing?

A

-save money by reducing the amount of cable or the number of network circuits that must be installed.

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17
Q

What are the four types of multiplexing?

A

-Frequency division multiplexing, Time division multiplexing, statistical time division multiplexing, wave length division multiplexing.

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18
Q

Describe FDM.

A
  • divides the circuit horizontally
  • divided into series of separate channels each transmitting on a different frequency.
  • exist on the media at the same time.
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19
Q

What are guardbands?

A

-used in FDM to separate frequencies from each other(unused).

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20
Q

Describe TDM.

A
  • divides the circuit vertically
  • one character taken from each computer in turn and transmitted down the circuit.
  • time allocated evenly even if there is not transmision
  • more efficient than FDM because it does not need guardbands.
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21
Q

Describe STDM.

A
  • capacity of the multiplexed circuit dos not need to equal the sum of the circuits it combines.
  • takes advantage of the fact that not all computers will need to transmit at the same time at their maximum speed.
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22
Q

What are benefits of STDM?

A

-provides more efficient use of the circuit and saves money.

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23
Q

What are disadvantages of STDM?

A
  • -needs internal memory to store incoming data if all users transmit at the same time.
  • need to add addressing to packets that increases overhead.
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24
Q

Describe WDM

A
  • wavelength division multiplexing.
  • version of FDM used in fiber-optic cables.
  • transmit different frequencies of light.
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25
Q

Describe Dense WDM.

A

-variant of WDM by adding TDM to WDM

26
Q

What is inverse-multiplexing?

A
  • combines several low-speed circuits to make them appear as one high-speed circuit.
  • T1 circuits for WANs
27
Q

What is BONDING?

A
  • Bandwidth on Demand Interoperability Network Group
  • standard that allows IMUX circuits to communicate with other IMUX circuits.
  • common in room to room video conferencing.
28
Q

What is DSL?

A
  • combines analog transmission and FDM to provide a set of voice and data circuits.
  • uses a combination of amplitude and phase modulate to provide the desired data rate.
29
Q

What is guided media?

A

-those in which the message flows through a physical media such as twisted pair wire, coaxial, etc.

30
Q

What is wireless media?

A

-broadcast through the air(unguided.)

31
Q

What are multimode fibe cables?

A
  • light can reflect inside the cable at many different angles.
  • plagued by excessive signal weakening(attenuation) and dispersion(different parts arrive at ddiferent times.
32
Q

What is graded-index multimode fiber?

A

-changes refractive properties of glass fiber so light arrives at the same time.

33
Q

What is single-mode fiber?

A
  • transmits a single direct beam of light through a cable that ensues the light reflects in only one pattern.
  • up to 100 kilometers
34
Q

What is microwave transmission?

A

-extremely high frequency radio communication beam
-line of sight path between two points.
-

35
Q

Describe satellite transmission.

A
  • geosynchronous: satellite remains stationary.

- has propagation delay.

36
Q

What is a coding scheme?

A

-the language that computers use to represent data.

37
Q

What is a character?

A

-a symbol that has a common, constant meaning.

38
Q

Describe ASCII

A
  • American Standard Code for Information Interchange
  • has 7-bit code with 128 valid character combinations
  • 80bit code with 256 valid combinations.
39
Q

Describe ISO 8859.

A

-8-bit code that includes ASCII codes and non-english letters.

40
Q

Describe Unicode.

A
  • UTF-8: 8-bit version

- UTF-16: 16 bit version

41
Q

What id parallel transmission.

A

-internal transfer of binary data where the bits of data element are transferred between mainmemory and CPU simultaneously on 8 separate connections.

42
Q

Describe serial transmission?

A

-stream of data is sent over a communication circuit sequentially in a bit-by-bit fashion.

43
Q

Describe digital transmission.

A

-transmission of binary electrical or light pulses in that it only has two possible states.

44
Q

Describe unipolar signaling?

A

-voltage is always positive or negative in which 0 volts transmits zeros and +5 volts transmits a 1.

45
Q

Describe bipolar signaling.

A

-the ones and zeros vary from a plus voltage to a minus voltage.

46
Q

Describe non return to zero (NRZ) signaling.

A

-alternates from +5 volts (indicates a 1) and -5 volts(indicates a zero) without returning to 0 volts.

47
Q

Describe return to zero signaling(RZ)

A

-always returns to zero volts after each bit before going to +5 volts for a 1 or -5 volts for a zero.

48
Q

Describe alternate mark inversion(AMI) signaling.

A

-0 is always sent using 0 volts, 1’s alternate between +5 volts and -5 volts.

49
Q

Describe manchester encoding.

A
  • bipolar signaling in which teh signal is changed from high to low or low to high in the middle of the signal.
  • high to low represents a 0
  • low to high represents a 1
50
Q

Describe analog transmission.

A

-signal sent over the transmission media continuously varies from one state to another in a wave-like pattern.

51
Q

Describe amplitude.

A

-in sound waves measured in decibels.

52
Q

Describe phase.

A

-direction in which the wave begins.

53
Q

Describe amplitude modulation.

A
  • amplitude shift keying
  • amplitude of the wave is changed.
  • one amplitued represents a 1 and another one represents a 0.
54
Q

Describe Frequency modulation.

A

-frequency shift keying
-each 0 or 1 represented by a certain number of waves per second.( a different frequency).
-

55
Q

Describe phase modulation.

A
  • phase shift keying(PSK)

- one phase is a 0, the other phase is a 1.

56
Q

What is QAM?

A
  • quadrature amplitude modulation.

- splits symbol into 8 different phases and two different amplitudes

57
Q

What is a baud?

A

-a unit of signaling speed used to indicate the number of times per second the signal on the communication circuit changes.

58
Q

Describe data rate.

A

-calculated by multiplying the number of bits sent on each symbol by the maximum sybol rate.

59
Q

What is bandwidth?

A

-difference between the highest and lowest frequencies in a band or set of requencies.

60
Q

Describe a modem.

A

-takes digital data from a computer in the form of electrical pulses and converts them into the analog signal that is need d for transmission over an analog voice-grade circuit.

61
Q

Describe codecs.

A

-used to send analog voice data over digital networks.

62
Q

Describe quantizing error>

A

-different between the original signal and the digitized signal.

IS 3413 (11 decks)

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