CPE 041 DATACOM Flashcards
The three major fields of electronics are _____. The largest is the _____.
computer, communications, and control
computer field.
_______ is the basic process of exchanging information.
Communication
Two of the main barriers to human communication are
language and distance.
An early form of long-distance communication is of waving a flag in which referred to as
semaphore.
Electronic communications came into being in the _____
late nineteenth century
The telegraph was invented in _____ and the telephone in _____.
1844, 1876.
In _____, radio was discovered, and it was demonstrated in _____.
1887, 1895
Most human communication is _____ even though there is a glut of _____ communication.
oral, written
The three main elements of any communications system are _____.
transmitter, receiver, channel or medium
The three major types of communications paths(media) are_____.
wire, radio, fiber-optic cable
The _____ converts the message into a form compatible with the selected medium.
transmitter
In most systems, a human generates a message that we call the
information, or intelligence signal.
______ is the general term applied to any interference that degrades the transmitted information.
Noise
is the medium by which the electronic signal is sent from one place to another.
communications channel or medium
In its simplest form, the medium may simply be a pair of wires that carry a voice signal from a microphone to a headset.
Electrical Conductors
The communication medium may also be a fiber-optic cable or “light pipe” that carries the message on a light wave.
Optical Media.
When ______ is the medium, the resulting system is known as _____.
free space, radio
is the broad general term applied to any form of wireless communication from one point to another.
Radio
________ is another collection of electronic components and circuits that accept the transmitted message from the channel and convert it back into a form understandable by humans.
receiver
Most communication equipment incorporates circuits that both send and receive. These units are commonly referred to as ________
Transceiver
Undesirable interference in communications is _____ which is added to the signal in the _____
Noise, Communication Channel
The transmission medium greatly _____ and ________ the transmitted signal.
degrades, attenuates
There are three ways in which electronic communication is classified:
one-way or two-way transmissions, analog or digital signals, and baseband or modulated signals.
The simplest way in which electronic communication is conducted is one way communications, normally referred to as ______.
simplex
The _________ system transmits information about the physical status of the satellite including its position and temperature.
telemetry
The bulk of electronic communications is ____.
two way
Such two-way communications is referred to as _________
Duplex
Another form of two-way communications is where only one party transmits at a time. This is known as ______
half duplex
An _________ is a continuously varying voltage or current.
analog signal
______ in contrast to analog signals, do not vary continuously, but change in steps or in discrete increments.
Digital signals
___________ are electronic techniques for transmitting information efficiently from one place to another.
Modulation and multiplexing
________ allows more than one signal to be transmitted concurrently over a single medium.
multiplexing
_______ makes the information signal more compatible with the medium
Modulation
Regardless of whether the original information signals are analog or digital, they are all referred to as ___________
baseband signals
Putting the original voice, video, or digital signals directly into the medium is referred to as _______
baseband transmission
_______ is the process of having a baseband, voice, video, or digital signal modify another higher frequency signal called the _______.
Modulation, carrier
Electromagnetic signals, which can travel through space for long distances, are also referred to as _________
radio-frequency (RF) waves, or just radio waves.
The carrier is fed to a circuit called a modulator along with the baseband intelligence signal. The intelligence signal changes the carrier in a unique way. The modulated carrier is amplified and sent to the antenna for transmission. This process is called _______.
broadband transmission
In ___________, the baseband information signal called the ________ varies the amplitude of the higher-frequency carrier signal.
amplitude modulation (AM), modulating signal
The three ways to make the baseband signal change the carrier sine wave are to __________
vary its amplitude, vary its frequency, or vary its phase angle.
In ___________, the information signal varies the frequency of the carrier. The carrier amplitude remains constant.
frequency modulation (FM)
Varying the phase angle produces ____________.
phase modulation (PM)
Two common examples of transmitting digital data by modulation are:
frequency-shift keying (FSK)and phase-shift keying (PSK).
Devices called ________ translate the data from digital to analog and back again.
modems(modulator-demodulator)
Both FM and PM are forms of __________.
angle modulation
At the receiver, the carrier with the intelligence signal is amplified and then demodulated to extract the original baseband signal. Another name for the demodulation process is _______.
detection.
_________ is the process of allowing two or more signals to share the same medium or channel.
Multiplexing
A _________ converts the individual baseband signals to a composite signal.
Multiplexer
There are three basic types of multiplexing
frequency division, time division, and code division.
In ___________, the intelligence signals modulate subcarriers on different frequencies that are then added together, and the composite signal is used to modulate the carrier.
frequency-division multiplexing
In ________________, the multiple intelligence signals are sequentially sampled, and a small piece of each is used to modulate the carrier.
time-division multiplexing
In ___________, the signals to be transmitted are converted to digital data that is then uniquely coded with a faster binary code.
code-division multiplexing
Three common sources of interference are _____.
the atmosphere, manufactured equipment, thermal agitation in components
One-way communications is called_____. An example is _____.
simplex, radio and TV broadcasting
Simultaneous two-way communications is called _____. An example is _____.
full duplex, telephone communications
Two-way communications where each parry takes turns transmitting is referred to as_____.
half duplex
Voice and video signals are continuous _____ voltages
analog
On/off or coded signals are referred to _____ as signals.
digital
Voice and video signals may be transmitted digitally if they are first passed through a(n) _____.
analog-to-digital converter
An original voice, video, or data voltage is called the _____ signal.
base band
To make the transmitted signal compatible with the medium, the process of _____ must be used where the _____ signal is impressed upon a higher-frequency signal called the_____.
Modulation. base band, carrier
Recovering the originally transmitted signal is called_____.
demulation or detection
The process of transmitting two or more baseband signals simultaneously over a common medium is called _____
multiplexing
Two methods of transmitting visual data over the telephone network are_____.
facsimile, teletext
A common household remote-control unit is the_____.
garage door opener
The signaling of individuals at remote locations is called _____.
paging
Performing, recording, and analyzing measurements at a distance is done with _____ equipment.
telemetry
Radio astronomy is based on the fact that stars and other heavenly bodies emit_____.
radio waves
List four ways radio is used in the telephone system _____
microwave relay, satellites, cordless phones, cellular phones
Radar is based on the use of _____ radio signals.
reflected
Underwater radar is called _____.
sonar (active)
The two types of sonar are _____.
active, passive
The radio communications hobby is called _____.
amateur or “ham” radio
Computers exchange digital data over the telephone network by using devices called _____.
modems
Limited interconnections of PCs and other computers in offices or buildings are called _____.
local area networks
Signals that travel through free space for long distances are called _____.
electromagnetic waves or radio-frequency (RF) waves
Radio waves are made up of _____ fields.
electric, magnetic
wavelength formula
lambda = c/f
Common power line frequencies of _____ and _____ Hz are in the _____ range.
50, 60, ELF
Audio signals are not transmitted by electromagnetic waves because
a. Antennas would be too long.
b. Audio signals do not radiate.
c. Simultaneous transmissions would interfere.
d. The frequency is too low.
(Choose all that apply.)
c
The human hearing range is approximately _____ to _____ Hz.
20, 20,000
The frequency range of the human voice is _____ to _____ Hz.
300, 3000
True or false. Radio transmissions do not occur in the VLF and LF ranges.
false
AM broadcast stations are in the _____ range.
Medium Frequency (MF)
535 to 1605 kHz
HF signals are also called _____.
short waves
TV (channels 2 to 13) and FM broadcasting is in the _____ part of the spectrum.
VHF
FM Broadcasting frequency range
88-108 Mhz
List five major uses of the UHF band.
land mobile, cellular telephones, military, radar and navigation, amateur radio
The SHF and EHF ranges are primarily used by _____ communications.
radar, satellite
Frequencies above 1 GHz are called _____.
microwaves
The frequencies just beyond the EHF range are called _____ waves.
millimeter
One micron is the same as _____ m.
1 / 1,000,000
Infrared signals are usually derived from _____ sources.
heat
The spectrum range of infrared signals is _____ to _____ m
0.7, 10
One angstrom is equal to _____ m.
1 / 10.000
The visible light range is from _____ to _____Ǻ.
4000,8000
Light signals can use two mediums in electronic communications _____.
fiber-optic cables, free space
The spectrum space occupied by a signal is called the _____.
bandwidth
The new signals above and below the carrier frequency produced by the modulation process are called _____.
sidebands
Wide-bandwidth signals must be transmitted at _____ frequencies.
higher
Percentage wise, there is less spectrum space at the _____ frequencies.
lower
Many communications electronics techniques are designed in order to conserve _____.
spectrum space
Electronic communications in the United States is regulated by a set of laws called the ____
Communications Act of 1934
The regulatory body for electronic communications in the United States is the _____.
Federal Communications Commission
Government and military communications are coordinated by the _____.
National Telecommunications and Information Administration
The electromagnetic spectrum is managed worldwide by the_____ organization.
International Telecommunications Union
Their _______ is measured in cycles per second (cps) or hertz (Hz).
frequency
The range of electromagnetic signals encompassing all frequencies is referred to as the_________.
electromagnetic spectrum
In electronics, ________ is the number of cycles of a repetitive wave that occurs in each period.
frequency
Frequency is measured in ________.
cycles per second (cps)
the unit of frequency is the _____, named for the German physicist ________, who was a pioneer in the field of electromagnetics.
hertz (Hz), Heinrich Hertz
_______ is the distance occupied by one cycle of a wave, and it isusually expressed in meters.
Wavelength
