A

A/B Switch

A switch that selects one of two inputs (A or B) for routing to a common output while providing adequate isolating between the two signals.

Automatic Frequency Control - AFC A circuit which locks an electronic component onto a chosen frequency. Automatic Gain Control - AGC A circuit that uses feedback to maintain the output of an electronic component at a constant level. Absolute Zero The coldest possible temperature at which all molecular motion ceases. It is expressed in degrees Kelvin as measured from absolute zero. Zero degrees Kelvin equals minus 273.16<198>C or minus 459.69<198>F. Access Control System - ACS Access Control System/s, comprising all conditional access components such as S/1, IDAC, ISAC, minicons, etc... Adaptation Header A block of data that forms an extension to a transport packet header. It may be of fixed format and/or of general data Adjacent Channel An adjacent channel is immediately next to another channel in frequency. For example, PAL channels 5 and 6 as well as 8 and 9 are adjacent. Agile Receiver A satellite receiver which can be tuned to any desired channel. Alignment The process of fine tuning a dish or an electronic circuit to maximize its sensitivity and signal receiving capability. AM An abbreviation for amplitude modulation Ambient Temperature The existing dry bulb temperature. Amplifier A device used to increase the power of a signal. Analog A system in which signals vary continuously in contrast to a digital system in which signals vary in discrete steps. Analogue-to-Digital Converter A circuit that converts analogue signals to an equivalent digital form. The varying analogue signal is sampled at a series of points in time. The voltage at each of these points is then represented by a series of numbers, the digital value of the sample. The higher this sampling frequency, the finer are the gradations and the more accurately is the signal represented Antenna A device that collects and focuses electromagnetic energy, i.e., contributes an energy gain. Satellite dishes, broadband antenna and cut-to-channel antennas are some types of antennas encountered. In the case of satellite dishes, gain is proportional to the surface area of the microwave reflector. Antenna Efficiency The percentage of incoming satellite signal actually captured by an antenna system. Aperture The collection area of a parabolic dish. Aperture Blockage An obstruction such as the feed assembly which causes a blockage of the incoming signal. Aspect Ratio The ratio of television screen width to height. The standard aspect ratio is 4 to 3. Attenuation The decrease in signal power that occurs in a device or when a signal travels to reach a destination point (path loss). Attenuator A passive device which reduces the power of a signal. Attenuators are rated according to the amount of signal attenuation. Audio Subcarrier The carrier wave that transmits audio information within a video broadcast signal. Satellite transmissions can relay more than a single audio subcarrier in the frequency range between 5 and 8.5 MHz. Automatic Brightness Control A television circuit used to automatically adjust picture tube brightness in response to changes in background or ambient light. Automatic Fine Tuning A circuit that automatically maintains the correct tuner oscillator frequency and compensates for drift and for moderate amounts of inaccurate tuning. Similar to AFC. Automatic Frequency Control (AFC) A circuit that locks onto a chosen frequency and will not drift away from that frequency. Automatic Gain Control (AGC) A circuit that locks the gain onto a fixed value and thus compensates for varying input signal levels keeping the output constant. Azimuth-Elevation (Az-El) Mount A dish mount that tracks satellites by moving in two directions: the azimuth in the horizontal plane and elevation up from the horizon. Azimuth A compass bearing expressed in degrees of rotation clockwise from true north. It is one of the two coordinates, azimuth and elevation, used to align a satellite dish. B Back Match The matching of the resistive values of the input and output of electronic devices to reduce signal reflection and ghosting. Also known as impedance matching. Back-Office Equipment A collective name for the elements responsible for the generation of EPG, conditional access information and system information Back Porch That portion of the horizontal blanking pulse that follows the trailing edge of the horizontal sync pulse. Band A range of frequencies. Band Separator A device that splits a group of specified frequencies into two or more bands. Common types include UHF/VHF, Hi/Lo-band and FM separators. This device is essentially a set of filters. Bandpass Filter A circuit or device that allows only a specified range of frequencies to pass from input to output. Bandwidth The frequency range allocated to any communication circuit. Baseband The raw audio and video signals prior to modulation and broadcasting. Most satellite headend equipment utilizes baseband inputs. More exactly, the composite unclamped, non-de-emphasized and unfiltered receiver output. This signal contains the complete set of FM modulated audio and data subcarriers Beamwidth A measure used to describe the width of vision of a dish. Beamwidth is measured as degrees between the 3 dB half power points Bird Jargon or nickname for communication satellites Bit Error Rate - BER The number of errors in a data stream usually expressed a ratio to the total number of bits in which an error occurs. For example, 1 in 10 7 or 10 -7 Bits per Second - BPS The number of bits transmitted each second Blanking Pulse Level The reference level for video signals. The blanking pulses must be aligned at the input to the picture tube. Blanking Signal Pulses used to extinguish the scan illumination during horizontal and vertical retrace periods. Block Downconversion The process of lowering the entire band of frequencies in one step to some intermediate range to be processed inside a satellite receiver. Multiple block downconversion receivers are capable of independently selecting channels because each can process the entire block of signals. BNC Connector A weatherproof twist lock coax connector standard on commercial video equipment and used on some brands of satellite receivers Boresight The direction along the principle axis of either a transmitting or a receiving antenna. Bouquet A group of services offered. The operator may also market a bouquet as a product such as `The Basic Bouquet.' Broadband A device that processes a signal(s) spanning a relatively broad range of input frequencies. BS Business System Business System Interface - BSI The interface providing access from a BS, converting the transaction to access control system format and then routing it to the correct access control system Buttonhook Feed A rod shaped like a question mark supporting the feed and LNA. A buttonhook feed for use with commercial grade dishes is often a hollow waveguide that directs signals from a feed to an LNA behind the dish. C CA Conditional Access. The control mechanism used to limit access by decoders to only the subscribed or free services on a multiplex CAT Conditional Access Table. A table that relates entitlement management message (EMM) data streams to the conditional access (CA) vendor(s) managing the decoder base. CATV An abbreviation for Community Antenna Television - another name for cable TV. CCD Charge coupled device. In this device charge is stored on a capacitor which are etched onto a chip. A number of samples can be simultaneously stored. Used in MAC transmissions for temporarily storing video signals. C-Band The 3.625 to 4.2 GHz band of frequencies at which some broadcast satellites operate. Carrier A pure-frequency signal that is modulated to carry information. In the process of modulation it is spread out over a wider band. The carrier frequency is the center frequency on any television channel. Carrier-to-Noise Ratio - C/N The ratio of the received carrier power to the noise power in a given bandwidth, expressed in decibels. The C/N is an indicator of how well an receive system will perform in a particular location, and is calculated from satellite power levels, dish gain and the system noise temperature. Cassegrain Feed System A dish feed design that includes a primary reflector, the dish, and a secondary reflector which redirects microwaves via a waveguide to a low noise amplifier. Channel A segment of bandwidth used for one complete communication link. Characteristic Impedance The impedance in ohms of a device in the path of a communication signal such as a cable, a connector or the input of an amplifier. Chrominance The hue and saturation of a color. The chrominance signal is modulated onto a 4.43 MHz carrier in the PAL television system and a 3.58 MHz carrier in the NTSC television system. Chrominance Signal The color component of the composite baseband video signal assembled from the I and Q portions. Phase angle of the signal represents hue and amplitude represents color saturation. Circular Polarity Electromagnetic waves whose electric field uniformly rotates along the signal path. Broadcasts used by Intelsat and other international satellites use circular, not horizontally or vertically polarized waves as are common in North American and European transmissions Clamp Circuit A circuit that removes the dispersion waveform from the downlink signal. Clamped Outputs Satellite receiver outputs that have the energy dispersal waveform removed. Unclamped outputs are often required as input to a decoder. Clarke Belt The circular orbital belt at 35 786 kilometers above the equator, named after the writer Arthur C. Clarke, in which satellites travel at the same speed as the earth's rotation. Also called the geostationary orbit. Color Bars A test pattern of specifically colored vertical bars used as a reference to test the performance of a color television. Coaxial Cable A cable for transmitting high frequency electrical signals with low loss. It is composed of an internal conducting wire surrounded by an insulating dielectric which is further protected by a metal shield. The impedance of coax is a product of the radius of the central conductor, the radius of the shield and the dielectric constant of the insulation. In most satellite and SMATV systems, coax impedance is 75 ohms. Color Sync Burst A <169>burst<170> of 8 to 11 cycles in the 4.43361875 MHz (PAL) or 3.579545 MHz(NTSC) color subcarrier frequency. This waveform is located on the back porch of each horizontal blanking pulse during color transmissions. It serves to synchronize the color subcarrier's oscillator with that of the transmitter in order to recreate the raw color signals. Composite Baseband Signal The complete audio and video signal without a carrier wave. Satellite signals have audio baseband information ranging in frequency from zero to 3400 Hertz. NTSC video baseband is from zero to 4.2 MHz. PAL video baseband ranges from 0 to 5.5 MHz. Composite Video Signal The complete video signal consisting of the chrominance and luminance information as well as all sync and blanking pulses. Companding A form of noise reduction using compression at the transmitting end and expansion at the receiver. A compressor is an amplifier that increases its gain for lower power signals. The effect is to boost these components into a form having a smaller dynamic range. A compressed signal has a higher average level, and therefore, less apparent loudness than an uncompressed signal, even though the peaks are no higher in level. An expander reverses the effect of the compressor to restore the original signal. Compressor A unit that accepts uncompressed video, audio and data and then digitizes and compresses these signals Compression System A collection of compressors, multiplexers and modulators that generate one multiplex signal Conditional Access - CA The encryption system CONE An abbreviation for the European continent. Contrast The ratio between the dark and light areas of a television picture. Control Systems Interface - CSI Conus An abbreviation for the continental United States. Cross Modulation A form of interference caused by the modulation of one carrier affecting that of another signal. It can be caused by overloading an amplifier as well as by signal imbalances at the headend. Cross Polarization Term to describe signals of the opposite polarity to another being transmitted and received. Cross-polarization discrimination refers to the ability of a feed to detect one polarity and reject the signals having the opposite sense of polarity Crosstalk Interference between adjacent channels often caused by cross modulation. Leakage can occur between two wires, PCB tracks or parallel cables. Customer Service - CS The group that interfaces directly with customers to answer any questions and deal with problems that arise. Customer Services Representative - CSR D Data/Voice Response Unit - DVRU dc Power Block A device which stops the flow of dc power but permits passage of higher frequency ac signals. Decibel (dB) The logarithmic ratio of power levels used to indicate gains or losses of signals. Decibels relative to one watt, milliwatt and millivolt are abbreviated as dBw, dBm and dBmV, respectively. Declination Offset Angle The adjustment angle of a polar mount between the polar axis and the plane of a satellite antenna used to aim at the geosynchronous arc. Declination increases from zero with latitude away from the equator. Decoder A circuit that restores a signal to its original form after it has been scrambled. Decoder Management A sub-system on the BS, managing all decoder/smartcard related information such as function testing, keysafing information, etc... Decoding Time Stamp - TS A 90 kHz referenced time stamp indicating when the contents of a packetized elementary stream (PES) packet should be decoded De-emphasis A reduction of the higher frequency portions of an FM signal used to neutralize the effects of pre-emphasis. When combined with the correct level of pre-emphasis, it reduces overall noise levels and therefore increases the output S/N ratio Demodulator A device which extracts the baseband signal from the transmitted carrier wave. Detent Tuning Tuning into a satellite channel by selecting a preset resistance. Digital Describes a system or device in which information is transferred by electrical <169>on-off,<170> <169>high-low,<170> or <169>1/0" pulses instead of continuously varying signals or states as in an analog message. Digital-to-Analog Converter A circuit that converts digital signals into their equivalent analog form. Digital Satellite TV - DStv - C- and Ku-band MultiChoice MPEG-2 DVB service Direct Broadcast Satellite (DBS) A term commonly used to describe Ku-band broadcasts via satellite directly to individual end-users. The DBS band ranges from 11.7 to 12.75 GHz. Direct-to-Home - DTH Dish Illumination Describes how a feed <169>sees<170> the surface of a dish as well as the surrounding terrain. Distribution Management A sub-system on the BS that manages all movements of serialized products such as ship-in, ship-out, depots, etc... Distribution System A communication system consisting of coax but occasionally of line-of-sight microwave links that carries signals from the headend to end-users. Domsat Abbreviation for domestic communication satellite. Downconverter A circuit that lowers the high frequency signal to a lower, intermediate range. There are three distinct types of downconversion used in satellite receivers: single downconversion; dual downconversion; and block downconversion. Downlink Antenna The antenna on-board a satellite which relays signals back to earth. Drifting An instability in a preset voltage, frequency or other electronic circuit parameter. DTH Direct-to-home satellite broadcasts. Dual-Band Feed A feed which can simultaneously receive two different bands, typically the C and Ku-bands. DVB Bouquet The DVB SI tables includes a Bouquet Association Table (the BAT). The DVB definition for a "bouquet" is "a group of services logically grouped together". The intention of the DVB Bouquet is usually to group services that are managed by one entity together. "DVB" is added before the name to distinguish it from the "SMS" bouquet. E Earth Station A complete satellite receiving or transmitting station including the dish, electronics and all associated equipment necessary to receive or transmit satellite signals. Also known as a ground station. Effective Isotropic Radiated Power (EIRP) A measure of the signal strength that a satellite transmits towards the earth below. The EIRP is highest at the center of the beam and decreases at angles away from the boresight. EPG Electronic Program Guide ES-Elementary Stream A stream carrying a single stream of, typically of presentation data, such as a single audio or video data stream Elementary Stream Clock Reference - ESCR Elementary Stream Clock ReferenceA 42-bit counter clocked at 27 MHz which is used for synchronizing data Elevation Angle The vertical angle measured from the horizon up to a target satellite. Encoder An entity that compressed a single data stream Energy Dispersal The modulation of an uplink carrier with a triangular waveform. This technique disperses the carrier energy over a wider bandwidth than otherwise would be the case in order to limit the maximum energy compared to that transmitted by an unclamped carrier. This triangular waveform is removed by a clamp circuit in a satellite receiver. Entitlement Control Message - ECM Data, used for conditional access, that describes the entitlements a decoder requires to receive a particular service Entitlement Management Message - EMM Data, used for conditional access, that defines to a particular decoder or subset of decoders what it(they) are entitled to receive Equalizing Pulses A series of six pulses occurring before and after the serrated vertical sync pulse to ensure proper interlacing. The equalizing pulses are inserted at twice the horizontal scanning frequency. Event An event is one particular transmission of a program. An event is known by its name, the service on which it is transmitted, the date and time of its broadcast and possibly additional information such as a part number. Events may be re-broadcast if the events are different EIT Event Information Table F F-connector A standard RF connector used to link coax cables with electronic devices. f/D Ratio The ratio of a dish's focal length to diameter. It describes dish depth. Feed A device that collects microwave signals reflected from the surface of a dish. It is mounted at the focus of all prime focus parabolic dishes. Field One half of a complete TV picture or frame, composed of 325 scanning lines. In the PAL broadcast system there are 50 fields per second. Filter A device used to reject all but a specified range of frequencies. A bandpass filter allows only those signals within a given band to be communicated. A rejection filter, the mirror image of a bandpass filter, eliminates those signals within a specified band but passes all other frequencies. Final Control Center FCC FM An abbreviation for frequency modulation Focal Length - The distance from the reflective surface of a parabola to the point at which incoming satellite signals are focused, the focal point. Footprint - The geographic area towards which a satellite downlink antenna directs its signal. The measure of strength of this footprint is the EIRP. Forward Error Correction - FEC FEC is a technique for improving the accuracy of data transmission. Excess bits are included in the out-going data stream so that error correction algorithms can be applied upon reception. On satellite links this is in the form of Reed-Solomon and convoluted Viterbi coding implemented at modulator/demodulator level. Frame One complete TV picture, composed of two fields and a total of 525 and 625 scanning lines in NTSC and PAL systems, respectively. Frequency The number of vibrations per second of an electrical or electromagnetic signal expressed in cycles per second or Hertz. Front-end Processor - FEP Front Porch The portion of the horizontal blanking pulse that precedes the horizontal sync pulse.     © 2003, Star Vision L.L.C <