Chapter 3

ASCII is the least popular code for data communications.

False

Fiber optic cable carries signals in traditional electrical form.

False

Frequency division multiplexing divides the circuit into a set of different time slots.

False

Frequency modulation refers to the changing of the height of the sound wave.

False

In a multipoint circuit configuration, each computer can use the circuit at the same time.

False

In simplex transmission, the data flows in both directions at the same time

False

Multimode fiber is capable of longer transmission distances than single mode fiber.

False

Multiplexing increases the cost of provisioning network circuits.

False

The amount of time it takes to switch between sending and receiving in half-duplex transmission is called the propagation delay.

False

Which of the following statements is correct?

Serial transmission is slower than parallel transmission.

Manchester encoding is a special type of bipolar signaling in which the signal is changed from high to low or from low to high in the middle of the signal.

True

Microwave transmissions require a line of sight between any two points.

True

Of all the media available, fiber optic provides the highest transmission speeds.

True

One form of interference with satellite transmission is called raindrop attenuation in which the transmissions are absorbed by heavy rain.

True

_________ is the basic physical layout of the circuit.

circuit configuration

_____________ refers to the difference between the original analog data and the approximation of that data using the techniques for translating from analog data to digital signals.

quantizing error

_____________ is not a form of modulation used to transform digital data into analog signals.

synchronous time division

Data compression can increase the throughput of a communication link.

True

Ethernet, a common LAN technology, uses Manchester encoding.

True

______ is a modem standard that uses Lempel-Ziv encoding to compress data.

V.44

___________ is commonly used to transmit phone conversations over digital networks.

VOIP

___________ refers to the spreading of the signal that different parts of the signal arrive at different times at the destination.

dispersion

If the highest frequency of a circuit is 10KHZ and the lowest frequency is 900 Hz, the bandwidth available for this circuit is :

9100 Hz

The "local loop" refers to the wires that run from the customer premises to the telephone switch of the telephone company.

True

The medium is the physical matter or substance that carries the voice or data transmission.

True

Which is not true about point-to-point circuits?

point-to-point circuits reduce the amount of cable required and use the circuit more efficiently than multipoint circuits.

The type of multiplexer that divides the circuit horizontally into different light frequencies that are transmitted simultaneously across many channels is a:

wavelength division multiplexer

When converting analog voice data to digital signals, Pulse Code Modulation typically samples the incoming voice signal _______ times per second.

8,000

____________ is one of the most commonly used coding schemes used in data transmission.

ASCII

Transmission speeds:

differ widely among media

In general, networks designed to transmit primarily computer data are likely to be ________.

digital

Two fundamentally different types of data are:

digital and analog

The ability to transmit in both directions, but only in one direction at a time is an example of _______________ transmission.

half-duplex

To get more "bandwidth" in a digital transmission, you must:

increase the range of frequencies available for a transmission

Frequency Division Multiplexing

operates by dividing the signal into different frequencies

Data is physically transmitted from one computer or terminal to another in the ________ layer.

physical

How many bits are required to sample an incoming signal 4000 times per second using 64 different amplitude levels?

6

When you send an email from the US to Europe, it likely is transmitted from one continent to another through one of the ______ that connect America and Europe.

submarine cables

Baud rate is the number of bits transmitted per second.

False

Fiber optic cable can only be used on LANs.

False

Newer telephone circuits, built during the last decade, offer higher quality because they were built using analog transmission.

False

Propagation delay is negligible with satellite transmission.

False

Radio, microwave and satellite are all examples of guided media.

False

Serial mode transmission is much faster than parallel mode transmission.

False

Wavelength division multiplexing can only used with copper cables.

False

Another term for the weakening of a signal over distance is:

attenuation

The _____________ of a circuit determines a circuit's capacity.

bandwidth

The predominant method of transferring information internally in a computer is via parallel mode.

True

Time division multiplexing is more efficient that frequency division multiplexing because the guardbands used in the frequency division multiplexing or not needed.

True

WDM is a version of FDM used in fiber-optic cables.

True

microwave transmission a. is a type of high frequency radio communication b. requires a clear line-of-sight path c. is typically used for long distance data transmission d. does not require the laying of any cable

all of the above

The height of a sound wave is called its:

amplitude

In general, older networks and local loops designed to transmit voice data are likely to be ________.

analog

Which of the following statements is true?

bandwidth is constant across any wire, therefore distance is not relevant to its capacity

Which type of digital signaling would experience fewer errors because it has more distinct signals?

bipolar

Which of the following would be considered a type of wireless media?

microwave

____________ refers to changing the shape of the sound wave in different ways to represent a 1 or a 0.

modulation

The acronym, Modem, stands for _________________.

modulator/demodulator

Which of the following is a characteristic of sound waves that can be modulated to convert digital data into analog signals?

phase

In which type of modulation is a 1 distinguished from a 0 by shifting the direction in which the wave begins?

phase modulation

Equipment used to transform analog voice signals to digital signals and digital signals to analog signals.

codec

Which of the following is not an important factor to consider when selecting media to be used in a network?

prestige value of the type of media

____________ is a modulation technique that combines two different amplitude combinations with eight different phase combinations modulation to send four bits per symbol.

quadrature amplitude modulation

When all bits of a character are transferred one after another, the bits are transferred in ___________ mode.

serial

A(n) __________ circuit is another name for a multipoint configuration.

shared

Time (non-statistical) division multiplexing differs from frequency division multiplexing because it:

splits the communication circuit vertically (with time slots) instead of horizontally

When sending four bits at a time using frequency modulation, the number of different frequency levels that would be needed would be _______.

16

Coaxial cable costs less and offers less shielding to electrical interference than twisted pair cable.

False

Digital transmission occurs when the signal sent over the transmission media constantly varies among an infinite number of states.

False

Digital transmission produces more errors than analog transmission.

False

Guided media refers to the type of media in which the message is broadcast through the air.

False

Multitasking means to break one high-speed physical communication circuit into several lower-speed logical circuits so that different devices can simultaneously use it.

False

Nonreturn to zero is a type of unipolar signaling

False

With modem communications, the receiving modem converts the incoming digital signal from the telephone line into an analog signal that can be understood by the computer.

False

With nonreturn to zero signaling, the voltage alternates between zero and a positive or negative voltage.

False

A walkie-talkie is an example of half-duplex transmission.

True

Amplitude, frequency and phase are all characteristics of a sound wave.

True

Coding schemes are groups of bits that translate into the "alphabet" of any given system.

True

Computers produce digital data whose values are binary: 0 or 1.

True

Digital transmission permits higher maximum transmission rates when compared to analog.

True

Frequency is the number of cycles per second and is expressed in Hertz.

True

In a multipoint circuit configuration, each computer has a dedicated circuit between itself and each of the other computers in the network.

True

In full-duplex transmission, two stations can send and receive simultaneously.

True

Statistical time division multiplexing does not require the capacity of the circuit to be equal to the sum of the combined circuits.

True

With respect to converting digital data into analog signals, AM stands for:

Amplitude Modulation

A codec converts an incoming digital signal to an analog signal for transmission over an analog network.

False

A physical circuit refers to the transmission characteristics of the connection, such as the speed at which data is being sent through the connection.

False

Based on the TIA/EIA 568-B structured cabling standard, the cabling that runs from the telecommunications closet to each work area is called backbone cabling.

False

The earliest type of fiber optic systems were:

Multimode

______________ refers to the time it takes for a signal to travel from sender to recipient (highly exaggerated with satellite transmission).

Propagation delay

A(n) ___________ divides one high-speed communication circuit into several lower speed circuits for the primary reason of saving communication line costs.

multiplexer

__________ is a line-of-sight type of wireless media.

microwave

The direction in which the sound wave begins is known as:

phase

A coding scheme that uses 10 bits to represent each character is capable of representing _________ different characters.

1024

If each sample uses 16 bits and the number of samples taken each second is 8000; then the transmission speed on the circuit is?

128 Kbps

The typical range of human hearing is:

20 to 14,000 Hz

A _________ is an FDM device that splits the physical circuit into three logical circuits (phone, upstream data, downstream data).

DSL Modem

___________ is not a type of digital signaling technique.

Data rate signaling

_____________ can be thought of as dividing the circuit horizontally.

Frequency division multiplexing

Which of the following is not a key advantage of digital transmission?

It permits only low transmission rates.

Ethernet uses

Manchester encoding

With which type of digital signaling does the signal always return to zero volts after each bit?

Return-to-zero signaling

One way to reduce quantizing errors is to increase the sampling rate of the analog signal.

True

Radio data transmission requires that each device has a radio receiver/transmitter and uses a specific frequency.

True

Signal bandwidth is the difference between the highest and lowest frequencies in a band.

True

____________ is used by IM and other applications that provide voice services over lower-speed digital circuits.

adaptive differential pulse code modulation

The representation of the character A by the group of 8 bits, 01000001, is an example of:

digital coding

Which of the following is the most secure wired media?

fiber optic cable

Which of the following media can best withstand harsh environmental conditions?

fiber optic cable

Which of the following media has the lowest error rates and the highest transmission speeds?

fiber optic cable

Having a conversation with someone using a cellular phone is an example of _________ transmission.

full-duplex

The two basic types of media are:

guided and wireless (radiated)

____________ refers to the transmission characteristics of the circuit.

logical circuit

The room that contains the cable termination points and the distribution frames is referred to as

telecommunications closet

The type of media usually installed on homes and businesses by the telephone company is called ____________.

twisted pair