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70 Cards in this Set
- Front
- Back
Volt
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Electrical current pressure
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Analog data signals
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Voltage varies continuously
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Properties of Analog signals
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Amplitude, frequency, wavelength, phase
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Amplitude
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Analog wave’s strength
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Frequency
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-Number of times amplitude cycles over fixed time period
-Measure in hertz (Hz) |
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Wavelength
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-Distance between corresponding wave cycle points
-Inversely proportional to frequency -Expressed in meters or feet |
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Phase
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Wave’s progress over time in relationship to fixed point
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Analog signal benefit over digital
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-More variable
-Convey greater subtleties with less energy |
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Drawback of analog signals
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-Varied and imprecise voltage
-Susceptible to transmission flaws |
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Pulses of voltages
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-Positive voltage represents a 1
-Zero voltage represents a 0 |
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Digital signal benefit over analog signal
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-More reliable
-Less severe noise interference |
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Digital signal drawback
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Many pulses required to transmit same information
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Overhead
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-Nondata information
-Required for proper signal routing and interpretation |
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Data relies on what?
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digital transmission
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What kind of signals can network connections only handle?
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analog signals
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A modem does what and is what?
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-Accomplishes translation
-Modulator/demodulator |
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Data modulation
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Technology modifying analog signals
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Carrier wave
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-Combined with another analog signal
-Produces unique signal Transmitted from one node to another |
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What is the purpose of a carrier wave?
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Convey information
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Information wave (data wave)
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-Added to carrier wave
-Modifies one carrier wave property |
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Frequency modulation
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-Carrier frequency modified by application of data signal
-Makes it conform to a specific pathway |
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Amplitude modulation
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-Carrier signal amplitude modified by application of data signal
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Simplex
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Signal transmission
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What direction does simplex travel?
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One direction
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Half Duplex
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Signal transmission
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What direction does half-duplex travel?
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-Both directions (one at a time)
-One communication channel -Shared for multiple nodes to exchange information |
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What direction does Full-duplex travel? And where is it used?
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-Both directions simultaneously.
- Used on data networks |
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Channel
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-Distinct communication path between nodes
-Separated physically or logically |
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What is the advantage of Full duplex?
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Increases speed
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Multiplexing
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Multiple signals travel simultaneously over one medium
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Subchannels
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Logical multiple smaller channels
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Multiplexer
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Combines many channel signals
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What is the abbreviation for Multiplexer?
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mux
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Demultiplexer
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- Separates combined signals
- Regenerates them |
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What is the abbreviation for Demultiplexer?
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demux
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time division multiplexing
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Divides channel into multiple time intervals
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Statistical multiplexing
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-Transmitter assigns slots to nodes according to priority, need
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Is TDM more efficient then Statistical multiplexing?
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No. Statistical multiplexing is more efficient than TDM.
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What is the abbreviation for time division multiplexing?
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TDM
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Frequency Division Multiplexing
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Unique frequency band for each communications subchannel
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What are the types of frequency division multiplexing?
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- Cellular telephone transmission
- DSL Internet access |
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Wavelength Division Multiplexing (WDM)
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-One fiber-optic connection
-Carries multiple light signals simultaneously |
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Dense Wavelength Division Multiplexing (DWDM)
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- Used on most modern fiber-optic networks
- Extraordinary capacity |
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Point-to-point transmission
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One transmitter and one receiver
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Point-to-multipoint transmission
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One transmitter and multiple receivers
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Broadcast transmission
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One transmitter and multiple, undefined receivers
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What is broadcast tranmisson used on?
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- wired and wireless networks.
- simple and quick. |
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Nonbroadcast
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One transmitter and multiple, defined receivers
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Throughput
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Capacity or bandwidth
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Bandwidth (strict definition)
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Measures difference between highest and lowest frequencies medium can transmit
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Baseband transmission
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Digital signals sent through direct current (DC) pulses applied to wire
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Give an example of baseband transmission.
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Ethernet
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Broadband transmission
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- Radiofrequency (RF) analog waves
- Uses different frequency ranges |
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Noise
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Any undesirable influence degrading or distorting signal
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EMI (electromagnetic interference)
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EMI/RFI (radiofrequency interference)
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Cross Talk
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near end cross talk (NEXT)
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What is a potential cause for cross talk?
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improper termination
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Environmental influences
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Heat
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List transmission flaws.
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1. EMI,
2. Cross talk, 3. Environmental influences. |
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Attenuation
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Loss of signal’s strength as it travels away from source
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Signal boosting technology
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Analog signals pass through amplifier
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What is also amplified in signal boosting technology?
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Noise.
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Regeneration
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Digital signals retransmitted in original form
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What device is used in digital signal regeneration?
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A repeater.
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What OSI layer do amplifiers and repeaters fall under?
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Layer 1 : Physical Layer
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Latency
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Delay between signal transmission and receipt
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What causes latency?
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- Cable length
- Intervening connectivity device |
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Round trip time (RTT)
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Time for packet to go from sender to receiver, then back from receiver to sender
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How is Round Trip Time measured?
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In milliseconds
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What are the characteristics of physical media?
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1. Throughput
2. Cost 3. Size and scalability 4. Connectors 5. Noise immunity Teaching Can Sure Cause Noise. |