What is the main function of DSLAM?

NETWORKING - PHYSICAL LAYER MCQ

• The physical layer is concerned with the movement of _______ over the physical medium
• The _______ is the physical path over which a message travels
• Before data can be transmitted, they must be transformed to ________
• A periodic signal completes one cycle in 0.001 s. What is the frequency?
• The physical layer concerns with
• The physical layer translates logical communication requests from the ______ into hardware specific operations
• The term ......... describes the position of the waveform relative to time 0
• In a frequency-domain plot, the horizontal axis measures the ________
• In a time-domain plot, the horizontal axis is a measure of ________
• If the bandwidth of a signal is 5 KHz and the lowest frequency is 52 KHz, what is the highest frequency?
• What is the bandwidth of a signal that ranges from 1 MHz to 4 MHz?
• As frequency increases, the period ________
• Given two sine waves A and B, if the frequency of A is twice that of B, then the period of B is ________ that of A
• A sine wave is ________
• If the maximum amplitude of a sine wave is 2 V, the minimum amplitude is ________ V
• A signal is measured at two different points. The power is P1 at the first point and P2 at the second point. The dB is 0. This means ________
• ________ is a type of transmission impairment in which the signal loses strength due to the resistance of the transmission medium
• _______ is a type of transmission impairment in which the signal loses strength due to the different propagation speeds of each frequency that makes up the signal
• _______ is a type of transmission impairment in which an outside source such as crosstalk corrupts a signal
• When propagation speed is multiplied by propagation time, we get the ________
• Data can be ________
• ______ data are continuous and take continuous values
• ______ data have discrete states and take discrete values
• Signals can be ________
• ____ signals can have an infinite number of values in a range
• ______ signals can have only a limited number of values
• Frequency and period are ______
• _______is the rate of change with respect to time
• ______ describes the position of the waveform relative to time 0
• A sine wave in the ______ domain can be represented by one single spike in the _____ domain
• A _________ sine wave is not useful in data communications; we need to send a _______ signal
• The _____ of a composite signal is the difference between the highest and the lowest frequencies contained in that signal
• A(n)_________ signal is a composite analog signal with an infinite bandwidth
• Baseband transmission of a digital signal is possible only if we have a ____ channel
• If the available channel is a ____ channel, we cannot send a digital signal directly to the channel
• For a ______ channel, the Nyquist bit rate formula defines the theoretical maximum bit rate
• For a ______ channel, we need to use the Shannon capacity to find the maximum bit rate
• ________ can impair a signal
• The _________ product defines the number of bits that can fill the link
• The portion of physical layer that interfaces with the media access control sublayer is called
• physical layer provides
• In asynchronous serial communication the physical layer provides
• The physical layer is responsible for
• A single channel is shared by multiple signals by
• Baud means?
• Which of the following devices takes data sent from one network device and forwards it to all devices on the network regardless of the intended recipient?
• Which of the following devices takes data sent from one network device and forwards it to the destination node based on MAC address?
• which of the following devices is used to connect different network segments and manage the traffic between them?
• Unipolar, bipolar, and polar encoding are types of _______ encoding
• ______ encoding has a transition at the middle of each bit
• ______ encoding has a transition at the beginning of each 0 bit
• PCM is an example of _______ conversion
• If the frequency spectrum of a signal has a bandwidth of 500 Hz with the highest frequency at 600 Hz, what should be the sampling rate, according to the Nyquist theorem?
• The Nyquist theorem specifies the minimum sampling rate to be_______
• Which of the following encoding methods does not provide for synchronization?
• Which encoding method uses alternating positive and negative values for 1s?
• Which quantization level results in a more faithful reproduction of the signal?
• Block coding can help in _______ at the receiver
• In _______ transmission, a start bit and a stop bit frame a character byte
• In asynchronous transmission, the gap time between bytes is _______
• __________ conversion involves three techniques: line coding, block coding, and scrambling
• _______ is the process of converting digital data to a digital signal
• ______ provides redundancy to ensure synchronization and inherent error detection
• _______ is normally referred to as mB/nB coding it replaces each m-bit group with an n-bit group
• _______ provides synchronization without increasing the number of bits
• Two common scrambling techniques are ________
• The most common technique to change an analog signal to digital data is called __________
• The first step in PCM is ________
• There are three sampling methods: __________
• _____ finds the value of the signal amplitude for each sample ____ finds the change from the previous sample
• While there is (are) only _____ way(s) to send parallel data, there is (are) three subclass(es) of serial transmission
• In ______ transmission, we send 1 start bit (0) at the beginning and 1 or more stop bits (1s) at the end of each byte
• In _________ transmission, we send bits one after another without start or stop bits or gaps. It is the responsibility of the receiver to group the bits
• The ________ mode provides synchronization for the entire stream of bits must. In other words, it guarantees that the data arrive at a fixed rate
• A _________ digital signal includes timing information in the data being transmitted
• In decoding a digital signal, the receiver calculates a running average of the received signal power, called the _______
• The signal rate is sometimes called the ____ rate
• The data rate is sometimes called the ___ rate
• In a _____ scheme, all the signal levels are on one side of the time axis, either above or below
• In ______ schemes, the voltages are on the both sides of the time axis. For example, the voltage level for 0 can be positive and the voltage level for 1 can be negative
• In _____, the level of the voltage determines the value of the bit
• In ______, the change or lack of change in the level of the voltage determines the value of the bit
• The idea of RZ and the idea of NRZ-L are combined into the ________ scheme
• In _______ encoding, the duration of the bit is divided into two halves. The voltage remains at one level during the first half and moves to the other level in the second half. The transition at the middle of the bit provides synchronization
• In ___________ there is always a transition at the middle of the bit, but the bit values are determined at the beginning of the bit. If the next bit is 0, there is a transition if the next bit is 1, there is none
• In Manchester and differential Manchester encoding, the transition at the middle of the bit is used for __________
• The minimum bandwidth of Manchester and differential Manchester is ____ that of NRZ
• In _______encoding, we use three levels: positive, zero, and negative
• The _____ scheme uses data patterns of size 2 and encodes the 2-bit patterns as one signal element belonging to a four-level signal
• The ______ scheme uses three levels (+V, 0, and -V) and three transition rules to move between the levels
• _____ substitutes eight consecutive zeros with 000VB0VB
• _____ substitutes four consecutive zeros with 000V or B00V
• ASK, PSK, FSK, and QAM are examples of ________ conversion
• AM and FM are examples of ________ conversion
• In QAM, both ________ of a carrier frequency are varied
• If the baud rate is 400 for a QPSK signal, the bit rate is ________ bps
• If the bit rate for an ASK signal is 1200 bps, the baud rate is ________
• If the bit rate for an FSK signal is 1200 bps, the baud rate is ________
• If the bit rate for a 16-QAM signal is 4000 bps, what is the baud rate?
• If the baud rate for a 64-QAM signal is 2000, what is the bit rate?
• Given an AM radio signal with a bandwidth of 10 KHz and the highest-frequency component at 705 KHz, what is the frequency of the carrier signal?
• ______ conversion is the process of changing one of the characteristics of an analog signal based on the information in the digital data
• Which of the following is not a digital-to-analog conversion?
• In ________, the amplitude of the carrier signal is varied to create signal elements. Both frequency and phase remain constant
• In _________, the frequency of the carrier signal is varied to represent data. Both peak amplitude and phase remain constant
• In ________, the phase of the carrier is varied to represent two or more different signal elements. Both peak amplitude and frequency remain constant
• A constellation diagram shows us the __________ of a signal element, particularly when we are using two carriers (one in-phase and one quadrature)
• Quadrature amplitude modulation (QAM) is a combination of ___________
• _______ uses two carriers, one in-phase and the other quadrature
• ________ conversion is the representation of analog information by an analog signal
• Analog-to-analog conversion is needed if the available bandwidth is _______
• Which of the following is not an analog-to-analog conversion?
• In _____ transmission, the carrier signal is modulated so that its amplitude varies with the changing amplitudes of the modulating signal
• In _____ transmission, the frequency of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal. The peak amplitude and phase of the carrier signal remain constant, but as the amplitude of the information signal changes, the frequency of the carrier
• In _____ transmission, the phase of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal
• In _______, the peak amplitude of one signal level is 0 the other is the same as the amplitude of the carrier frequency
• How many carrier frequencies are used in BASK?
• How many carrier frequencies are used in BFSK?
• How many carrier frequencies are used in BPSK?
• How many carrier frequencies are used in QPSK?
• The constellation diagram of BASK has ______ dots
• The constellation diagram of BPSK has ______ dots
• The constellation diagram of QPSK has ______ dots
• The constellation diagram of 16-QAM has ______ dots
• The Federal Communications Commission (FCC) allows ______kHz for each AM station
• The Federal Communications Commission (FCC) allows ______ kHz for each FM station
• Which of the following layer decide the transmission rate in a Network?
• What is the main function of DSLAM?
• What is the use of Bridge in Network?
• Repeater operates in which layer of the OSI model?
• Which of the following is not the possible ways of data exchange?
• This kind of data transmission allows data to be transmitted in both directions on a signal carrier at the same time
• What is the difference between a switch and a hub?
• MAC address is also known as __________
• Repeater operates in which layer of the OSI model
• Repeater function in the ...................... layer
• A repeater takes a weakened or corrupted signal and ............... it
• What device separates a single network into two segments but lets the two segments appear as one to higher protocols?
• Which of the following is used for modulation and demodulation?
• Which of the following types of channels moves data relatively slowly?
• Which of the following device is used to connect two systems, especially if the systems use different protocols?
• The synchronous modems are more costly than the asynchronous modems because
• The cheapest modems can transmit
• Computers cannot communicate with each other directly over telephone lines because they use digital pulses whereas telephone lines use analog sound frequencies. What is the name of the device which permits digital to analog conversion at the start of a long distance transmission?
• Demodulation is a process of
• Demodulation is the process of
• A devices that links two homogeneous packet-broadcast local networks, is
• The physical layer, in reference to the OSI model, defines
• Which of the following device copies electrical signals from one Ethernet to another?
• For connecting modem, a computer must be equipped with a port that conforms to the RS-232 standard of the Electronic Industries Association of America. What do the letters \'RS\' stand for?
• If communication software can be called the traffic cop of a micro communication system, then what should the modem be called?
• The fundamental requirements of private-to-public network interconnection methods which need to be provided in gateways is/are
• Interconnected networks need communication processors such as switches, routers, hubs, and gateways. Select the best fit for answer:
• What is the name of the device that converts computer output into a form that can be transmitted over a telephone line?
• Now-a-days computers all over the world can talk to each other. Which is one of the special accessories essential for this purpose?
• Devices on one network can communicate with devices on another network via a
• What is the name of the device that connects two computers by means of a telephone line?
• The _____ layer is the layer closest to the transmission medium
• Which of the following allows devices on one network to communicate with devices on another network?
• RS-449/442-A/423-A is
• A form of modulation In which the amplitude of a carrier wave is varied in accordance with some characteristic of the modulating signal, is known as
• A modulator converts a _____ signal to a(n) _____ signal
• Repeaters are often used on an 802.3 network to help strengthen the signals being transmitted. As with the length of segments and the number of segments, a limit exists as to how many repeaters can be used between any two nodes. What is the maximum number of repeaters that can be used?
• A modem that is attached to the telephone system by jamming the phone\'s handset into two flexible receptacles in the coupler?
• Which of the following statements is correct?
• A modem is connected in between a telephone line and a
• A smart modem can dial, hang up and answer incoming calls automatically. Can you tell who provides the appropriate instruction to the modem for this purpose?
• In a synchronous modem, the digital-to-analog converter transmits signal to the
• Which of the following connectivity devices is used to extend a network on a purely mechanical basis?
• Who invented the modem?
• Propagation time is equals to
• Period is the inverse of
• The black and white TV is an example of
• The level of the signal is inversely proportional to the
• The Nyquist formula gives us any signal level while Shannon capacity gives us the
• Increasing the levels of a signal may reduce the
• If signal does not change at all, its frequency is
• A period of 100 ms in microseconds would be equals to
• Analog data refers to information that is
• We send a voice signal from a microphone to a recorder, the transmission is
• The unit that is used to express the state of a signal is
• The data rate depends upon
• Bit rate is measured in
• Periodic analog signals can be classified as
• Digital data refers to the information that is
• Conversion of digital signal to analog signal is
• A sine wave is defined by
• A digital signal is a composite analog signal with
• Digital signals are represented in
• In data communications, the non periodic signals
• The term that refers to loss of strength of a signal is called
• The value of the decibel is positive, if signal is
• The completion of one full pattern is called a
• The term that describes the position of the waveform relative to time 0 is
• Bit Rate is the number of bits sent in
• In baseband transmission, the required bit rate is proportional to the
• Change over a long span of time means
• The term that refers to infinite no of values in the range is
• The propagation speed of electromagnetic signals depends on the
• The transmission impairment that refers to a signal with high energy in a very short time is
• Bit length can be defined in terms of
• If a noiseless channel with a bandwidth of 3000 Hz transmitting a signal with two signal levels the maximum Bit rate would be
• Sine wave can be represented by three parameters
• The range of frequencies a channel can pass is called bandwidth in
• When there is heavy traffic on the network, the queuing time is
• The time required for a bit to travel from source to destination is
• In data communications, we use periodic analog signals and
• The range of frequencies contained in a composite signal is its
• In real life, we cannot have a
• A transmission media can have signal impairment because of
• The bandwidth of a composite signal is the difference between the highest and
• The relationship between amplitude and frequency can be represented by
• Frequency is expressed in
• Given the frequency 24Hz the corresponding period would be
• The power in our house can be represented by
• In induced noise, the impairment is created by sources like
• Data to be transmitted must be transformed into
• SNR stands for
• SNR (signal to noise ratio) is equals to
• One Picoseconds (PS) is equivalent to
• We cannot send the digital signal directly to the channel, when the channel is
• The difference in the delay of the signal may create a difference in
• Signal to Noise Ratio is the ratio of the two
• According to Fourier analysis, any composite signal is a combination of sine waves with
• How many factors data rate limit depends on
• Consider the below figure. What are the bits transmitted for the Unipolar system?
• If a periodic signal is decomposed into five sine waves with frequencies of 100, 300, 500, 700, and 900 Hz, what is its bandwidth?
• Assume we need to download text documents at the rate of 100 pages per second. What is the required bit rate of the channel?
• A digitized voice channel is made by digitizing a 4-kHz bandwidth analog voice signal. We need to sample the signal at twice the highest frequency (two samples per hertz). We assume that each sample requires 8 bits. What is the required bit rate?
• What is the bit rate for high-definition TV (HDTV)?
• A device is sending out data at the rate of 1000 bps. How long does it take to send a file of 100,000 characters?
• A file contains 2 million bytes. How long does it take to download this file using a 56-Kbps channel?
• We need to send 265 kbps over a noiseless channel with a bandwidth of 20 kHz. How many signal levels do we need?
• Calculate the theoretical highest bit rate of a regular telephone line. The signal-to-noise ratio is usually 3162
• Calculate the theoretical channel capacity. If SNR(dB) = 36 and the channel bandwidth is 2 MHz
• A channel has a 1-MHz bandwidth. The SNR for this channel is 63. What is the appropriate bit rate?
• A channel has a 1-MHz bandwidth. The SNR for this channel is 63. What is the appropriate signel level?

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