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Comm 240 Exam 1


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Antennas (Radiators)
Electrical conductors with Alternating Current; Most efficient when height=radio wavelength being broadcast
Netword Cloud
shows the connections of all the different hosts
Meeting collaborative figures out available times for meeting other members
Frequency [Radio Wave]
the rate of alternating current (slow or fast)
best measure to how many households have access to a given technology; percent of marketplace use
AM Radio
3 Parts: Carrier Wave; Adjacent Sidebands (USB/LSB are directly proportional to range of frequencies); Bandwidth
removes redundancy in signals and saves bandwidth with increased capacity
Wave Propogation
positive and negative aspects of a wave act as its poles. as each wave is emitted, it repels/propels the preceding wave before it causing radio wave transmission
3 layers of technology
Hardware, Software, Content
FM radio Stations are classified by
power and height from the ground
Direct Waves
Higher Frequency (VHF, UHF, SHF, EHF); Towers are less expensive; Prone to interference when line of sight is blocked
picture quality
determined by resolution and amount of colors allowed in picture (bits)
Social Information Processing Theory
people make adoption decisions and other evaluations of technologies based upon objective characteristics of the technology
Binary Digits
Bits, count but skip all numbers without 1 or 0 in it. 1, 10, 11, 100, 101, 110, 111....
a popular tool for adding clientside animation and interactivity to webpages -more control than Javascript; -supports unique application and graphic formats (makes manipulation of graphical objects easier but text harder)
Pulse Code Modulation (PCM)
a common audio encoding method that demonstrates a 3 step analog to digital conversion process
Waves bending
Uses and Gratifications Theory
explores the uses and benefits of technology
Power [Radio Wave]
the amount of electric current put into the radio wave (a little or a lot) - amplitude
Internet radio relies on
Internet Protocol (IP) HTTP is not necessary for simply audio
Frequency Modulation (FM)
carrier changes from high to low frequency based upon wave length/freq
FM Radio Spectrum
channels are 20 kHz wide... 20x wider than AM; use guardbands to protect from interference; simplexing/multiplexing
FM Radio
1933 Armstrong modulated frequency which produces a clear sound
needs line of sight; parabolic dish used to focus incoming radio waves onto antenna in the middle
Representing a Picture
draw a grid of rectangles over an image to create pixels
Motivating Factors
provide an incentive for the adoption of new technology
buy new technology while very expensive
Satellite Radio
broadcast from space; crystal clear or not there; monthly subscription
grew together to reach almost 100% penetration. no displacement.
Lossy Compression
represent bitstrings that are only slightly different with a single so that info is lost (e.g. JPEG)
Google Docs
stores documents online (like a microsoft office on the internet)
a sophisticated platform independent programming language -most programs are computer specific (extremely flexible but slow/hard to program)
Motion Pictures
Thomas Edison (Late 19th Century)....10 year gaps between technological discoveries=sounds, color, widescreen, 3D, IMAX, digital
how fine the grid is.... smaller squares gives the illusion of continuity
Binary Codes
represents quantized signal level
Problems with AM
very inefficient (alot of wasted power with LSB); poor sound quality (low bandwidth/lots of static)
Sound Recordings
Phonautograph (Late 19th Century), Edison's phonograph, Records, CDs, MP3
instructions guiding the operation of the hardware
dictates where on the electromagnetic spectrum wave is going
Peer to Peer (P2P)
each host acts as a client in some exchanges and a server in others (ex IM, limewire)
Sky Waves (Skip Waves)
Medium Frequency; Daytime/Nighttime Differences; Go through Ionosphere during day (very effective) but skips and causes interference at night
Sales Figures
not a reliable way of comparing how many people actually use technology (ex varying prices)
Anti-Aliasing Images
Use color to make up for missing resolutions (makes for a smoother appearance)
the process of converting a continuous analog signal into a binary digital signal of 0s and 1s
Frequency Influence on Wave Propagation
long wavelength=wave follows curvation of Earth's surface; short wavelength=wave travels in a straight line and ignores Earth's curvation
line of sight helps, but not required; antenna places on roof, hill, supporting tower and doesnt need to be as tall
standard built on top of digital broadcasting technology (DTV) with higher definition and sound
computers exchanging information with one another
World Wide Web
a system of interlinked hypertext documents (one type of content transported over the internet)
LF, MF, HF Antennas
does NOT need a line of sight to transmit; almost always use all steel towers, typically 1/4 height of wavelength
S shaped Curve for Adoption of Innovation
innovators, major adopters, laggards
false frequencies in the reconstructed signal as a result of undersampling
Digital Signal
discrete wave that is either on or off -rectangular waveform-
3 Measures for Measuring Media Access and Consumption
Sales Figures, Number of Units Sold, Penetration
3 types of radio waves
ground, direct, sky/skip
messages communicated through or mediated by the lower layers
Sociotechnical System
communication systems are largely defined by societal factors: laws, technical standards, social conventions, individual skills
range of frequencies used by a signal. more bandwidth=better sound quality
Quantized Signal
has a fixed number of levels
Enabling Factors
often focus on new technical capabilities, but social factors as well
AM Radio Stations are classified by
Digital Audio Recording
converting from analog to a digital signal
Ground Waves
Lower Frequency (LF, MF, HF); Hug Earth's Surface; Most stable type of wave; Low interference; Large expensive towers; Best conditions for travel distance: lower freq, higher power, wetter ground
Alexander Graham Bell (Late 19th Century).... wireless msgs, mobile radio phone for Detroit police cars, cellphones, displacement of landlines
Digital Radio
less bandwidth and less compression; multiple audio streams on a single station with no interference but low quality when signal is weak
Limiting Factors
opposite to enabling factors that constrain communication... can be technical or social
occurs at regular intervals (digital isnt choppy because of large sampling per second)
Domain Name System (DNS)
handles IP address look ups
Compression Drawbacks
over compression can cause reduction of quality and aliasing in audio and video
sharing files across a secure company network
allows transmission of information using waves by altering characteristics of a periodic carrier signal to enable it to carry information
Why convert to digital?
1. no static 2. transmission errors can be fixed 3. compression requires less bandwidth 4. enhanced security encryption
Inhibiting Factors
opposite of motivating, these provide a disincentive for buying new technology (too expensive)
Digital Audio Playback
converting back to original analog signal (bit string to soundwave via digital to analog converter and speakers)
1906 invented by Lee de Forest- Early Radio... allowed for signal amplification but was still difficult to hear
Radio Frequency Spectrum
Managed by the FCC - LF, MF, HF, VHF, UHF, SHF, EHF
"Lock" digital data automatically using a secret key (e.g. Rotation Cipher = Rot n)
refers to the unification of diverse communication technologies (integration of mass media, telephone and computers)
a simple language for providing client-side web page interactivity (can do complex things but is not as flexible)
those who do not purchase new technologies until it is completely necessary
Music Sales
consistently rose until late 1990s due to illegal downloading/file sharing
a heterogenous mix of computer networks that speak a common language and agree to help deliver messages for each other
Digital TV
FCC transition Februrary 17, 2009
the common language for transporting messages across the internet
History of Technology
telephone, motion pictures, sound recordings, radio, television, computers, video games
Bits can be
recorded and transmitted
Motion Picture Representation
a sequence of images
hosts in an exchange have different responsibilities -client display results; -servers return results (search engine, email)
Amplitude Modulation (AM)
varies the amplitude or power of a signal while frequency of carrier is left untouched
a text based addressing system linked to IP address
a language built on top of TCP/IP that is used to deliver web content (send/receive webpages)
Analog Signal
continuous wave that vary in amplitude and rate -curvilinear waveform-
distance a wave travels in one period; inversely proportional to frequency
Radio Data Systems (RDS)
allows compatible radio to display metadata (song titles, station call letters) and transmits with FM stations using multiplexing
Federal Communication Commission (FCC)
They allocate which technologies and which companies can broadcast on which wavelengths
Modulating Wave
message that you want to send
each picture cell is represented with a bitstring that codes the colors of that cell
collaboration editing tool
IP Address
a unique 32 bit number for every computer on the internet
a set of rules stating how communication can take place between computers and electronic documents
Factors for the AM to FM Radio Move
1. better sound quality 2. decreasing availability of AM channels 3. FCC restricted many AM stations from simulcasting their signals on FM to open up more of the spectrum for FM
Electromagnetic Spectrum
ranges from 1 Hz to infinite.... only small lower freq section can be used for communication transmission
Online party list and RSVPs
Original Signal
has continuous amplitudes
Magnetic part to Electromagnetic energy
AC creates radiation
computer connected to other computers by a network
the physical equipment
access/share files between computers
# of Units Sold
better measure than sales figures but can also over inflate usage (radio in a house vs. radios actually used)
Lossless Compression
eliminate long strings of identical bits or bit that do not change between frames
Properties of Radio Waves
Power, Frequency. Independent of one another.
Coder and Decoder: software used to convert digital back to analog for playback (must use same standards as recording)
The FCC Mandate
FCC est. by Comm Act of 1934 assign radio station frequencies that do not interfere with each other
Electromagnetic waves can be
recorded and transmitted
Alternating Current
electric current that repeatedly and regularly alternates
The AM Dial
carrier waves occur at 10kHz intervals from 540kHz to 1600kHz
Major Adopters
very rapid uptake with lower price (the average American)
Google Calendar
Online calendar with daily events
extra samples add no new information (sounds the same) but the file is bigger than need be
stand way of representing text characters with number or bits (series of letters can be represented as collection of adjacent bitstrings)
Movie Theater Attendance
steadily increased until 1950 with advent of television
Analog Audio Recording
Converting one analog signal into another (soundwave to electromagnetic wave via microphone)
Critical Mass Theory
value of technology goes up with number of users (ex. being first to use facebook is not so great... more users have greater value for each user.)
important variation in audio signal between samples... causes aliasing
Hertz (Hz)
Frequency measurement; the number of complete wave cycles in a second. kHz=cycles per thousandth of a second
a text based language used to describe webpages (hypertext markup language)
Regenerative Circuit
1913 Edwin Armstrong invented this radio amplifier so home radios could be heard across a room
Analog Audio Playback
Converting back to original analog signal (EM Wave to soundwave via speaker)
when one technology replaces a previous one
Network Speed Depends on....
Speed of connection to the internet and speed of messages on the internet

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