Adjacent
Channels Any of two TV channels are considered adjacent when their frequencies
are next to each other in frequency or channel number. Amplifier A
device that boosts the strength of a television signal. Analog A method
of signal transmission in which information is relayed by continuously altering
the wave form of the electromagnetic current. Now used in AM radio or most voice
telephone circuits. In telephone transmission, the signal being transmitted voice,
video or image is "analogous" to the original signal. Antenna A wireless
system component that converts wired electrical energy to wireless radio waves,
and directs them through the air in some pattern. Antenna Array An
antenna comprising a number of radiating elements, generally similar, which are
arranged and excited to obtain directional radiation patterns. Attenuation
In general terms, a reduction in signal strength. Automatic Frequency
An arrangement whereby the frequency of an oscillator is automatically maintained
within specified limits. Automatic Gain Control A circuit for automatically
controlling amplifier gain in order to maintain a constant output voltage with
a varying input voltage within a predetermined range of input-to-output variation.
A process by which gain is automatically adjusted as a function of input or other
specified parameter. Axial Ratio The ratio of the axes of the polarization
ellipse. Backhaul Point-to-point video transmission from a remote
site back to a central site for further distribution. Band A clearly
defined range of radio frequencies dedicated to a particular purpose. Bandwidth
The number of cycles per second (Hertz) expressing the difference between the
lower and upper limiting frequencies of a frequency band; also, the width of a
band of frequencies. The range of frequencies within which the performance of
the antenna, with respect to some characteristic, conforms to a specified standard.
Greater bandwidth generally provides for a more robust system because changes
in the installation environment will not degrade antenna performance. Bandwidth
A range of frequencies on the electromagnetic spectrum. Beam width
In a plane containing the direction of the maximum of a beam, the angle between
the two directions in which the radiation intensity is one half the maximum value
of the beam. Bi-directional Communications between two points where
each point both transmits and receives. Bird Slang for communications
satellite. Bounce Sudden variations in picture presentation (brightness,
size, etc.,) independent of scene illumination. Broadband A descriptive
term for evolving digital technologies that provide consumers a signal switched
facility offering integrated access to voice, high-speed data service, video-on-demand
services and interactive delivery services. Broadband In television
system use, a device having a bandpass greater than the band of a single VHF television
channel. CATV Cable TV A service through which subscribers pay to have
local television stations and other programs brought into their homes from the
antenna via coaxial cable C-Band The 3.7 - 4.2 GHz (Gigahertz) frequency
band is used for the distribution of programming by virtually all satellite/cable
networks. There are 22 C-Band satellites in operation over North America today.
They range in power from 5-11 watts per transponder, requiring receive antennas
of 5-12 feet in diameter. Beginning in 1992, the fleet was gradually replaced
with higher powered (10-17 watt) satellites. This allows the average size of a
C-Band installation to be reduced to 90 inches in diameter. Channel
A 6 MHz wide portion of the RF spectrum carrying TV video and audio carriers.
Clarke Belt The name given in honor of Arthur C. Clarke, to the orbit 22,300
miles directly above the equator where satellites can maintain a stationary position
in relation to the earth. Also called geostationary orbit. Coax Short
for coaxial cable.
Coaxial
Antenna An antenna comprised of an extension to the inner conductor of a coaxial
line and a radiating sleeve which in effect is formed by folding back the outer
conductor of the coaxial line. Coaxial Cable A type of cable capable
of transmitting a range of frequencies with low signal loss. Commonly used for
transmitting video and audio in security systems. Coaxial Cable A type
of cable commonly used in cable (CATV) and direct broadcast satellite (DBS) television
systems. Composed of two concentric conductors (an inner wire and a braided shield)
separated by a dielectric material. The whole thing is usually wrapped in another
insulating layer and an outer protective layer. Most coaxial cable used in CATV
and DBS applications has an impedance of 75 ohms. A coaxial cable has great capacity
to carry great quantities of information. It is typically used to carry high-speed
data and in CATV (multiplexed TV stations.) Compression A term used
to denote reducing the amount of bandwidth needed to transmit video or audio,
thus increasing the capacity of a satellite transponder. The reduction in gain
at one level of a picture signal with respect to the gain at another level of
the same signal. Crosstalk An undesired signal from a different channel
interfering with the desired signal. dB Decibels A technique for expressing
voltage, power, gain, loss, or frequency in logarithmic form against a reference.
Typical references include volts, Watts or Ohms. An analog unit of measure of
signal strength, volume or signal loss due to resistance as expressed in logarithmic
form. A measure of the power ratio of two signals. In system use, a measure of
the voltage ratio of two signals, provided they are measured across a common impedance.
Hz. Decibels are calculated using the expression: dB = 10*log(x/y)
dBi A ratio of decibels to an isotropic antenna that is commonly used
to measure antenna gain. The greater the dBi value, the higher the gain and, as
such, the more acute the angle of coverage. dBmV A signal measurement
whereby 0 dBmV equals 1000 microvolts across 75 ohms. A recommended signal level
for a TV to receive is 10 dBmV. DBS Direct Broadcast Satellite A high-powered
satellite that transmits or retransmits signals which are intended for direct
reception by the public. The signal is received by a small (typically 18-inch
diameter) dish mounted on the sides of homes or on other buildings. Signal content
is generally television programing. Decibel A unit to measure the relative
levels of current, voltage or power. This is the scale used to measure the strength
of a TV signal. An increase of 3 dB indicates a doubling of power. Demodulation
The process for retrieving an information signal that has been modulated onto
a carrier. Descrambler Set-top box. A device which corrects a signal
(often video) that has been intentionally distorted to prevent unauthorized viewing.
Used with satellite TV systems. Digital A method of storing, converting
and sending data in the form of binary digits ( 0 or 1). In displays, the use
of digits for direct readout. In telecommunications, in the recording or in computing,
digital is the use of a binary code to represent information. Analog signals (like
voice or music) are encoded digitally by sampling the voice or music analog signals
many times a second and assigning a number to each sample. Recording or transmitting
information digitally has two major benefits. The signal can be reproduced more
precisely so digital transmission is much "cleaner" than analog transmission.
The second major benefit of digital is that the electronic circuitry to handle
digital is getting cheaper and more powerful. Digital Recording Technology
that enables video images to be stored on a hard drive or other digital storage
medium rather than on an analog medium such as a videotape. Dipole
A type of low gain antenna consisting of two (often internal) elements. Directional
Antenna An antenna having the property of radiating or receiving electromagnetic
waves more effectively in some directions than others. Dish cover A
cylindrical weather protection device. Dish Size Refers to the diameter
of the dish, or antenna, used in satellite reception. Dish Slang term
for antenna. Distortion The deviation of the received signal waveform
from that of the original transmitted waveform. Distribution Amplifier
A device that provides several isolated outputs from one looping or bridging input,
and has a sufficiently high input impedance and input-to-output isolation to prevent
loading of the input source. Diversity Antenna An intelligent system
of two antennas that continually senses incoming radio signals and automatically
selects the antenna best positioned to receive it. Downlink To receive
from a satellite also, the dish used for reception. DSL Digital Subscriber
Line A generic name for a family of evolving digital services to be provided
by local telephone companies to their local subscribers. Such services go by different
names and acronyms - ADSL (Asymmetric Digital Subscriber Line), HDSL (High Bit
Rate Digital Subscriber line) and SDSL (Single Pair Symmetrical Services). Such
services propose to give the subscriber up to eight million bits per second one
way, downstream to the customer and somewhat fewer bits per second upstream to
the phone company.
DTH Direct-To-Home.
A term referring to all home satellite platforms. DVR Digital Video
Recorders (same as PVR). Dynamic Range The difference between the
maximum acceptable signal level and the minimum acceptable signal level.
Embedded Antenna Typically an antenna that is enclosed into a product's
housing or case, or one that is not readily discernible by a casual observer.
The antenna forms an integral, inseparable part of the product. Encryption/
Decryption Encryption is the process of electronically altering a video and/or
audio from its original condition. Decryption is the process of returning the
video and/or audio to its original condition. EPG Electronic Programming
Guide. F-connector The final piece of hardware on a cable designed
for CATV or DBS or other signal distribution applications. It is cylindrical with
a center pin sticking out, that plugs into the set-top box, cable ready TV, satellite
receiver, or VCR. Feedhorn The part of the satellite system that collects
and focuses satellite signals reflected by the antenna. Fiber Optics Fiber
A shortened way of saying "fiber optic." Fiber is made of very pure glass. Digital
signals, in the form of modulated light, travel on strands of fiber for long distances.
The big advantage that fiber has over copper is that it can carry far, far more
information over much, much longer distances. Field of View The maximum
angle of view that can be seen through a lens or optical instrument. Field
One of the two equal but vertically separated parts into which a television frame
is divided in an interlaced system of scanning. A period of 1/60 second separates
each field start time. Filter A circuit that selects the frequency
of desired channels through the use of band pass, low pass, and high pass filters
remove certain unwanted signals to make room for the insertion of a new modulated
TV channel Frequency Response The range of band of frequencies to which
a unit of electronic equipment will offer essentially the same characteristics.
Frequency The number of times an electromagnetic wave goes through
a complete cycle in one second, measured in Hertz. FSS Fixed Satellite
Service. Gain An increase in voltage or power, usually expressed in
dB. In a given direction, 4 pi times the ratio of the radiation intensity in that
direction to the net power accepted by the antenna from the connected transmitter.
A measure of amplification expressed in dB. Gain of an amplifier is usually specified
at the highest frequency of operation. Ghost A spurious image resulting
from an echo. GHz Gigahertz; one trillion cycles per second (a measure
of frequency). Ground Plane A conducting or reflecting plane functioning
to image a radiating structure. GSO Geosynchronous Orbit; satellites
in geosynchronous orbit travel around the earth in an area approximately 22,300
miles from the surface at the same rate that the earth turns, therefore completing
one revolution every 24 hours. Headend A cable TV systems control
center where incoming signals from satellites and other sources are put into the
system. (Head End) The originating point of a signal in cable TV systems. At the
head end, you'll often find large satellite receiving antennae. A central control
device required within some LAN systems to provide such centralized functions
as remodultaion, re-timing, message accountability, connection control, diagnostic
control, and access. Headend Homerun Wire The Homerun Wire is most
often a single wire (usually an RG6 or RG59 coaxial cable) that runs from each
apartment building's meter room to each apartment and is designed to deliver television
or telephone services. Some of the modern day Homerun Wires are being used to
deliver all services, cable and satellite television, telephone and fax and high-speed
Internet connections. High Definition Television Technology that significantly
increases the resolution of digital video signals offering vastly improved picture
quality over the current NTSC standard. Hum Electrical disturbance
at the power supply frequency or harmonics thereof. Hybrid Satellite
A satellite that carries two or more different communications payloads (i.e.,
C-Band and Ku-Band). Hz Hertz Cycle per second; a measure of electromagnetic
frequency that represents the number of complete electrical waves in a second.
One kilohertz (kHz) is one thousand cycles per second; one megahertz (MHz) is
one million; one gigaHertz (GHz) is one billion. Impedance (input or output)
The input or output characteristic of a system component that determines the type
of transmission cable to be used. The cable used must have the same characteristic
impedance as the component. Expressed in ohms. Video distribution has standardized
on 75-ohm coaxial and 124-ohm balanced cable. Impulse Pay-Per-View
Technology that allows the consumer to purchase a movie or special event instantly
via a computerized order processing center. This technology allows for the processing
of a high volume of orders in a short time period. Input Impedance
The impedance presented by an antenna at its terminals. Inside Wiring
That wiring located inside your premises or building. Inside wiring starts at
the telephone or cable company's Demarcation Point and extends to the individual
extensions. Traditionally, Inside Wiring was installed and owned by the installing
company. Interference Extraneous energy which tends to interfere with
the reception of the desired signals. IPG Interactive Programming
Guide. IRD(integrated receiver decoder) A device capable of receiving
and tuning satellite signals. The output of the receiver can be either Baseband
video for use with video monitors or RF for use with standard TV sets. Isolation
Amplifier An amplifier with input circuitry and output circuitry designed
to eliminate the effects of changes made at either upon the other. Isolation
Between Antennas A measure of power transfer from one antenna to another -
the ratio of power input to one antenna to the power received by the other, usually
expressed in decibels. Isotropic A hypothetical antenna having equal
radiation intensity in all directions. Jitter Small, rapid variations
in a waveform due to mechanical disturbances or to changes in the characteristic
of components. Supply voltages, imperfect synchronizing signals, circuits, etc.
kA-Band A higher frequency than Ku-Band, operating from 18 to 31 gigaHertz.
kHz Kilohertz. Ku-Band The 11.7-12.7 GHz (Gigahertz) frequency
band. This band has been split into 2 segments by the FCC. The first is the 11.7-12.2
GHz band known as FSS (Fixed Satellite Service) There are 22 FSS Ku-Band
satellites in orbit over North America today. They range in power from 20-45 watts
per transponder, requiring a 3-5 foot antenna for clear reception. The 12.2 -
12.7 GHz segment is known as BSS (Broadcast Satellite Service). Satellites in
this band range in power from 100 - 200 watts per transponder, allowing the use
of receive antennas as small as 12-18 inches. L-Band Potion of electromagnetic
spectrum commonly used in satellite and microwave applications with frequencies
in the 390 MHz to 1550 MHz range. The GPS (global positioning system) frequencies
are in the L-Band. GPS uses 1227.6 MHz and 1575.42 MHz LEO Low Earth
Orbit; satellites placed in orbit less than 22,300 miles above the earth.
Light Electromagnetic radiation detectable by the eye, ranging in wavelength
from about 400 to 750 nm. Line Amplifier An amplifier for audio or
video signals that feeds a transmission line; also called program amplifier.
Line of Sight An unobstructed straight line between two transmitting devices.
Line of sight is typically required for long-range directional radio transmission.
Due to the curvature of the earth, the line of sight for devices not mounted on
towers is limited to 16 miles (26 km). LNB Low Noise Block convertor.
System devise used to amplify and convert satellite signals into frequencies sent
to the tuner. Loop Through Also called looping. The method of feeding
a series of high impedance circuits (such as multiple monitor/displays in parallel)
from a pulse or video source with a coax transmission line in such a manner that
the line is bridged (with minimum length stubs) and that the last unit properly
terminates the line in its characteristic impedance. This minimizes discontinuities
or reflections on the transmission line. Loss A reduction in signal
level or strength, usually expressed in dB. Power dissipation serving no useful
purpose. Low-Frequency Distortion Distortion effects which occur at
low frequencies. In television, generally considered as any frequency below the
15.75 kHz line frequency. Matrix Switcher A device that routes any
of its inputs to any of its outputs. Inputs are normally cameras or alarms, and
outputs are normally recorders or monitors. A matrix switcher allows a user to
control what information is sent where within a large security network. MHz
Megahertz, a measure of frequency in millions (mega) of cycles per second.
MMDS Multipoint Multi-channel Distribution Service. MMDS is a way of distributing
cable television signals, through microwave, from a single transmission point
to multiple receiving points. Often used as an alternative to cable-bases cable
TV. An MMDS service, "in digital form, will provide more than 100 channels to
a radius of approximately 40 miles from the transmitter. The MMDS transmitter
delivers video to homes that are in its 'line of sight.' MMDS transmissions are
limited by the terrain and foliage of a given market. The microwave signal is
received by an antenna on the subscriber's home, then sent down coaxial cable
to a box atop the customer's TV set. The box decodes and decompresses the digital
signal." MMDS is increasingly being called "Wireless Cable." Modems Acronym for
Modulator/Demodulator. Conventional modems comprise equipment which converts digital
signals to analog signals and vice versa. Conventional PC modems outputs data
in the form of "1's" and "0's" which are represented by varying levels of voltage.
The modem converts the digital data signal into variations of the analog sine
wave so the data can be transmitted over the device with a digital bit stream.
The modulation techniques include some combination of Amplitude Modulation (AM),
Frequency Modulation (FM) and Phase Modulation (PM), also known as Phase Shift
Keying (PSK). Used in combination, these techniques allow multiple bits to be
represented with a single (or single set) OF SINE WAVES). In this fashion, compression
is accomplished, which allows more data to be transmitted in the same period of
time and which therefore reduces the connect time and the associated cost of the
data transfer. Modulation The process of superimposing an information
signal onto a carrier for transmission. The process where some characteristic
of one signal is varied in accordance with another signal. The carrier may be
modulated in three fundamental ways: by varying the amplitude, called amplitude
modulation; by varying the frequency, called frequency modulation; by varying
the phase, called phase modulation. The creation of a TV channel from a video
and audio source for transmission over a distribution coaxial cable network.
Modulator The electronic equipment required to combine video and audio
signals and convert them to TV radio frequencies (RF) for distribution to other
equipment (including televisions) on a cable network. MPEG Motion Pictures
Experts Group. Multiplexer A device that can accept a number of camera
inputs and almost simultaneously display them on a single monitor. Can be used
to transmit multiple cameras over the same transmission medium. A device that
accepts video signals from more than one camera and encodes them onto one signal
that is sent to a digital recorder or VCR. The multiplexer also decodes the recording
so it can play back video from one camera or several cameras at once on a monitor.
NAB National Association of Broadcasters. NCTA National Cable
Television Association. Noise The word "noise" originated in audio
practice and refers to random spurts of electrical energy or interference. In
some cases, it will produce a "salt-and-pepper" pattern over the televised picture.
Heavy noise is sometimes referred to as "snow". NTSC Abbreviation
for National Television Systems Committee. A committee that worked with the FCC
in formulating standards for the present day United States color television system.
A television industry group that develops standards for standard television broadcasting
and receiving equipment in the US. Off-Air Reception of a TV signal
that has been broadcast through the air by a TV station. Omni-directional
Antenna An antenna having an essentially non-directional pattern in azimuth,
and a directional pattern in elevation. Output The signal level at
the output of an amplifier or other device. Packet Data A process where stored
data is transmitted in discrete units, called packets, allowing for more efficient
use of channel capacity and reliability of transfer. Patch Cords Cables
used to interconnect electronic equipment often terminated with modular or RCA-type
plugs. Patch Panel A panel where circuits are terminated and facilities
provided for interconnecting between circuits by means of jacks and plugs.
PCS Personal Communications System. Peak Pulse Amplitude The
maximum absolute peak value of a pulse, excluding those portions considered to
be unwanted, such as spikes. Peak-to-Peak The amplitude (voltage)
difference between the most positive and the most negative excursions (peaks)
of an electrical signal. A full video signal measures one volt peak to peak.
Personal Video Recorder (PVR) Product that tracks viewing habits, records
programs and has other interactive features such as pause and rewind. PIFA
Planer Inverted F Antenna. Polarization In a given direction, the polarization
of the wave radiated by the antenna. Alternatively, the polarization of a plane
wave incident from the given direction which results in maximum available power
at the antenna terminals. PVR Personal Video Recorder. A consumer device
which uses a hard disk drive to record television programs based on the user's
preferences. QPSK Quaternary Phase Shift Keying; a digital modulation
scheme used in transmission communications that allows increased sending capacity
Radiation Pattern (antenna pattern) A graphical representation of
the radiation properties of the antenna as a function of space coordinates.
Radome An enclosure for protecting an antenna from the harmful effects
of its physical environment, generally intended to leave the electrical performance
of the antenna unaffected. Resolution (horizontal) The amount of resolvable
detail in the horizontal direction in a picture. It is usually expressed as the
number of distinct vertical lines, alternately black and white, which can be seen
in a distance equal to picture height. RF
Radio Frequency The area (or band) of the electromagnetic spectrum where most
radio communication takes place, typically from 100 KHz to 100 GHz. A frequency
at which coherent electromagnetic radiation of energy is useful for communication
purposes. Analog electrical signals sent on cable or over the air. Conventional
(broadcast) television and radio, as well as cable TV, deliver RF signals to your
television/radio. Ripple Amplitude variations in the output voltage
of a power supply caused by insufficient filtering. Satellite Antenna
(Dish) A parabolic antenna that collects satellite signals. C-Band antennas
range in size from 5-12 feet in diameter; K-Band antennas range from 18 inches
to 6 feet. Satellite Programmer A company that produces, packages
or distributes video, audio, and/or data services for distribution to the home
satellite dish and cable markets. SCPC Single Channel Per-Carrier;
an economical way to get multiple signals on one transponder. Scrambling
Altering a video signal transmission so it can not be received without an
authorized operating decoder. Signal Leakage (Leakage) is a cable
TV term. Leakage occurs when certain radio frequencies ooze out of the CATV's
coaxial cable in such strength that they are evident outside the home. They might
be sufficiently strong to interfere with aircraft navigation. Leakage is really
a shielding problem. Smart Card Technology that allows for the upgrade
of encryption security through the use of a consumer-installable card containing
a new computerized security code. SMATV Dish & DBS Dish The dish-like
antenna used to receive satellite signals. SMATV Satellite Master
Antenna Television; or private cable; a miniature cable system that receives programming
by one satellite dish and serves an entire housing complex, hotel or apartment
etc. Splitter A passive device (one with no active electronic components)
which distributes a television signal carried on a cable in two or more paths
and sends it to a number of receivers simultaneously. Spread Spectrum
A means of transmission in which encoded information is carried in discrete packages
of information, then spread over a wide bandwidth for transmission to specific
receivers that filter out the coded material. Stubby Antenna A short
thick monopole. Sun Outage When the sun passes behind a satellite in
relation to the earth and its energy momentarily interferes with the satellite
signals. This happens two times each year during spring and fall equinox.
Superstation A local TV station whose signal is satellite delivered to
cable systems and backyard antennas across the country. Switcher A
simplified SEG that selects and mixes video signals from two or more sources.
TDMA Time Division Multiple Access is one of several technologies used
in digital wireless transmissions that increases the efficiency of the network
by allowing a greater number of simultaneous transmissions. Networks using TDMA
assign 6 time slots for each frequency channel. Devices using the wireless network
send bursts of information that are reassembled at the receiving end. Terrestrial
In communications parlance, this refers to earth, land or ground-based telecommunications
systems. TNC (RP-TNC) A connector type unique to Net WORLD radios
and antennas. Part 15.203 of the FCC rules covering spread-spectrum devices limits
the types of antennas that may be used with transmission equipment. In compliance
with this rule, Net WORLD, like all other wireless LAN providers, equips its radios
and antennas with a unique connector to prevent attachment of non-approved antennas
to radios. Transceiver A combination transmitter and receiver.
Transients Signals which exist for a brief period of time prior to the
attainment of a steady-state condition. These may include overshoots, damped sinusoidal
waves, etc. Transponder A satellite component that receives and retransmits
a TV signal or perhaps many narrower-band data or audio channels. TVRO
(Television Receive-Only) An industry term used to describe a home satellite
system that only receives and does not transmit satellite television signals.
UHF Ultra High Frequency The part of the radio spectrum from 470 MHz
to 806 MHz, including TV channels 14 through 83. Uplink To transmit
to a satellite for relay; also, the dish used to transmit. Vertical Resolution
The number of horizontal lines that can be seen in the reproduced image of a television
pattern. VHF Very High Frequency. The part of the radio spectrum from
54 to 88 MHz and 174 to 216 MHz, which includes TV channels 2 through 13.
Video Amplifier A wideband amplifier used for passing picture signals.
Video Band The frequency band width utilized to transmit a composite
video signal. Video Signal (Non-Composite) The picture signal. A signal
containing visual information and horizontal and vertical blanking (see also Composite
Video Signal) but not sync. Wireless Transmission A technology in
which electronic devices send information to receivers using radio waves rather
than wiring. Wireless A system without outside wires, for example cellular
telephony or satellite television. Zapping Changing the channel by
remote control during a program to avoid a commercial. Zipping Fast-forwarding
through commercials when playing back a program on a VCR. |