Cable Terms and Definitions
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Active:
Any circuit containing amplifying devices, such as tubes or transistors.
Adjacent Channel:
Any of two TV channels are considered adjacent when their video carriers, either off-air or on a cable system, are 6 MHz apart. FM signals on a cable system, two channels apart are adjacent when their carriers are 400 to 600 KHz apart.
Allocations:
The assignments of frequencies by the FCC for various communications uses (e.g., television, radio, land-mobile, defence, microwave, etc.) to achieve a fair division of the available spectrum and minimize interference among users.
Amplifiers:
A device used to boost the strength of an electronic signal. Amplifiers are spaced at intervals throughout a cable system to rebuild the strength of television signals which weaken as they pass through the cable network.
Antenna:
A device used to transmit or receive broadcast signals.
Antenna Preamplifier:
A small amplifier, usually mast-mounted, for amplifying weak signals to a level sufficient to compensate for down-lead losses and to supply sufficient input to system control devices.
Anti-siphoning:
FCC rules which prevent cable systems from "siphoning off" programming for pay cable channels that otherwise would be seen on conventional broadcast TV. "Anti-siphoning" rules state that only movies no older than three years and sports events not ordinarily seen on television can be cablecast.
Audio:
The aural components of a television signal; also, aural broadcasting such as AM and FM radio.
Automatic Gain Control (AGC):
A circuit which automatically controls the gain of an amplifier so that the output signal level is virtually constant for varying input signal levels.
Automatic Slope Control:
Automatic correction of changes in slope by compensating circuitry.
Back Porch:
That portion of the composite picture signal which lies between the trailing edge of the horizontal sync pulse and the trailing edge of the corresponding blanking pulse.
Bandwidth:
A measure of spectrum (frequency) use or capacity. For instance, a voice transmission by telephone requires a bandwidth of about 3000 cycles per second (3KHz). A TV channel occupies a bandwidth of 6 million cycles per second (6MHz). Cable system bandwidth occupies 50 to 300 MHz on the electromagnetic spectrum.
Blanking (Picture):
The portion of the composite video signal whose instantaneous amplitude makes the vertical and horizontal retrace invisible.
Block Tilt:
A method of setting the output levels of all low-band channels at a given number of dB lower than high-band channels.
Bridging Amplifier or Bridger:
An amplifier which is connected directly into the main trunk of a CATV system but isolated from it. It provides service into the distribution or feeder systems.
Broadband:
A general term used to describe wide bandwidth equipment or systems which can carry a large proportion of the electromagnetic spectrum. A Broadband communications system can accommodate all broadcast and many other services.
Broadcaster's Service Area:
Geographical area encompassed by a station's signal. (See Predicted Grade A Contour and Predicted Grade B Contour).
Broadcasting:
Transmitting electromagnetic signals in a multidirectional pattern over the air.
Cable Powering:
A method of supplying power to solid-state CATV equipment by using the coaxial cable to carry both signal and power simultaneously.
Cable TV:
Previously called Community Antenna Television (CATV). A communications system which distributes broadcast programs and original programs and services by means of coaxial cable.
Cablecasting:
To originate programming over a cable system. Includes public access programming.
CARS (Community Antenna Relay Service):
The 12.75-12.95 GHz microwave frequency band which the FCC has assigned to the CATV industry for use in transporting television signals.
Carriage:
A cable system's procedure of carrying the signals of television stations on its various channels. FCC rules determine which signals cable systems must or may carry.
Cartridge:
Container for recorded programming designed to be shown on a television receiver. The cartridge contains a reel of motion picture film, videotape or electronically embossed vinyl tape, blank or recorded, and uses an external take-up reel.
Cassette:
A self-contained package of reel-to-reel blank or recorded film, videotape or electronically embossed vinyl tape which is continuous and self-rewinding. Similar to a cartridge, but of slightly different design.
Certificate of Compliance:
The approval of the FCC that must be obtained before a cable system can carry television broadcast signals.
Channel:
In television, a single path or section of the spectrum 6 MHz wide, which carries a television signal.
Channel Capacity:
The maximum number of 6 MHz channels which can be simultaneously carried on a CATV system.
Chrominance Signal:
That portion of the NTSC colour television signal which contains the colour information.
Clipping:
The sheering off of the peaks of a signal. For a picture signal, this may affect either the positive (white) or negative (black) peaks. For a composite video signal, the sync signal may be affected.
Closed Circuit:
A system of transmitting TV signals in which the receiving and originating equipment are directly linked by cable, microwave or telephone lines, without broadcasting through the air.
Coaxial Cable:
Copper or copper-sheathed aluminum wire surrounded by an insulating layer of polyethylene foam, used by CATV systems. The insulating layer is covered with tubular shielding composed of tiny strands of braided copper wire, or a seamless aluminum sheath, and protective outer skin. The wire and the shielding react with each other to set up an electromagnetic field between them. This system reduces frequency loss and gives cable its great signal-carrying capacity.
Co-channel:
Any two or more TV signals are considered co-channel when their video carriers, either off-air or after conversion by CATV equipment, occupy the same TV channel.
Colour Burst:
In NTSC colour, normally refers to a burst of approximately 9 cycles of 3.6MHz subcarrier on the back porch of the composite video signal. This serves as a colour synchronizing signal to establish a frequency and phase reference for the chrominance signal.
Colour Subcarrier:
In NTSC colour, the carrier whose modulation sidebands are added to the monochrome signal to convey colour information; i.e., 3.6MHz (3.579545MHz)
Combining Network:
A passive network which permits the addition of several signals into one combined output with a high degree of isolation between individual inputs. It may be a power or frequency combiner.
Common Carrier:
Any point-to-point communications relay service available to the general public at non-discriminatory rates. The carrier cannot control message content (e.g., telephone companies).
Composite Video Signal:
The complete video signal. For monochrome, it consists of the picture signal and the blanking and synchronizing signals. For colour, additional colour synchronizing signals and colour picture information are added.
Compression:
An undesired decrease in amplitude of a portion of the composite video signal relative to that of another portion. Also, a less than proportional change in output of a circuit for a change in input level. For example, compression of the sync pulse means a decrease in the percentage of sync during transmission.
Compulsory License:
Legislation requiring copyright holders to license users of copyrighted material (CATV operators) on a uniform basis and for a stipulated fee.
Contrast:
The range of light and dark values in a picture, or the ratio between the maximum and minimum brightness values. A high-contrast picture would contain intense blacks and whites; a lower-contrast picture would contain only shades of grey.
Converter:
A device used to convert non-VHF television signals into standard VHF channels. Cable systems often install converters where more than 12 channels are relayed on a single cable. Converters also protect signals from the interference of strong local signals.
Critical Distance or Cable Length:
The length of a particular cable which causes a worst-case reflection if mismatched; depends on velocity of propagation, attenuation of cable, and frequency.
Cross-Modulation:
A form of signal distortion in which modulation from one or more r-f carrier(s) is imposed on another carrier.
Cross-Ownership:
Ownership of two or more kinds of communications outlets by the same individual or business. The FCC prohibits television stations and telephone companies from owning cable systems in their service areas. Television networks are prohibited from owning cable systems anywhere in the U.S.
Crosstalk:
An undesired signal interfering with the desired signal.
Cutoff Frequency:
That frequency beyond which no appreciable energy is transmitted. It may refer to either an upper or lower limit of a frequency band.
Delay Distortion:
Distortion resulting from nonuniform speed of transmission of the various frequency components of a signal; i.e., the various frequency components of the signal have different times of travel (delay) between the input and the output of a circuit.
Differential Gain:
In colour TV, the change in gain, expressed in dB, for the 3.58 MHz colour sub-carrier as the level of the luminance signal is varied from blanking to white.
Differential Phase:
Variation in phase of the colour subcarrier of a TV signal as the level of the luminance signal is varied from blanking to white.
Directional Coupler:
A high-quality tapping device providing isolation between tap and output terminals.
Distant Signal:
TV signals which originate at a point too far away to be picked up by ordinary home reception equipment; also signals defined by the FCC as outside a broadcaster's license area. Cable systems are limited by FCC rules in the number of distant signals they can offer subscribers.
Distortion:
The departure, during transmission and amplification, of the received signal wave form from that of the original transmitted wave form.
Distribution Plant:
The hardware of a cable system -- amplifiers, trunk cable and feeder lines, attached to utility poles or fed through underground conduits like telephone and electric wires.
Distribution System:
The part of a CATV system used to carry signals from the headend to subscriber's receivers. Often applied, more narrowly, to the part of a CATV system starting at the bridger amplifiers.
Downstream:
Signals travelling from the headend to subscriber's homes.
Dual Cable:
A method of doubling channel capacity by using two cables installed side by side to carry different signals.
ETV (Educational Television Station):
A noncommercial television station primarily devoted to educational broadcasting.
Earth Stations:
Ground terminals that use antennas and associated electronic equipment to transmit, receive and process communications via satellite. Future cable systems may be able to interconnect by domestic communications satellites, creating regional and national cable networks.
Easement:
The right to use land for a specific purpose, such as laying cable.
Echo (or Reflection):
A wave which has been reflected at one or more points in the transmission medium, with sufficient magnitude and time difference to be perceived in some manner as a wave distinct from that of the main or primary transmission. Echoes may be either leading or lagging the primary wave and appear on the picture monitor as reflections or "ghosts."
Education Channel:
FCC rules require cable systems in the top 100 markets to set aside one channel for educational uses, to be available without cost for the "developmental period." The developmental period of a CATV system runs for five years from the time that subscriber service began, or five years after the completion of the basic trunk line.
Electromagnetic Spectrum:
A continuous range of frequencies of electromagnetic radiation (i.e., oscillating electrical and magnetic energy which can travel through space). Within the spectrum, waves have some specified common characteristics; the TV broadcast spectrum, for instance, ranges from 45 to 890 MHz. (see Frequency)
Equalization:
A means of modifying the frequency response of an amplifier or network, thereby resulting in a flat overall response.
Equalized Loss:
Any loss in CATV systems caused by coaxial cable; also, insertion loss of components designed to match cable loss characteristics.
Equalizing Pulses:
Pulses of one half the width of the horizontal sync pulses which are transmitted at twice the rate of the horizontal sync pulses during the blanking intervals immediately preceding and following the vertical sync pulses. The action of these pulses causes the vertical deflection to start at the same time in each interval, and also serves to keep the horizontal sweep circuits in step during the vertical blanking intervals immediately preceding and following the vertical sync pulse.
Exclusivity:
The provision in a commercial television film contract that grants exclusive playback rights for the film or episode to a broadcast station in the market it serves. Under the FCC's rules cable operators cannot carry distant signals which violate local television stations' exclusivity agreements.
Facsimile:
The electronic transmission of pictures, charts, graphs, etc., from one place to another by radio, telegraphy or telephone. With special facsimile equipment, a home television receiver may be able to deliver mail and newspapers by cable.
Feeder Line:
Intermediate cable distribution lines that connect the main trunk line to the smaller house drops that lead into residences.
Field:
One half of a complete picture (or frame) interval, containing all of the odd or even scanning lines of the picture.
Field Frequency:
The rate at which a complete field is scanned, nominally 60 times a second.
Filter:
A circuit that selects the frequency of desired channels. Used in trunk and feeder lines for special cable services such as two-way operation.
Flat Loss:
Equal loss at all frequencies, such as caused by attenuators.
Flat Outputs:
Operation of a CATV system with equal levels of all TV signals at the output of each amplifier.
Frame:
One complete picture consisting of two fields of interlaced scanning lines.
Frame Frequency:
The rate at which a complete frame is scanned nominally 30 frames per second.
Franchise:
Contractual agreement between a CATV operator and the governing municipal authority. Under federal regulation a franchise, certificate, contract or any other agreement amounts to a license to operate.
Frequency:
The number of times an electromagnetic signal repeats an identical cycle in a unit of time, usually one second. One Hertz (Hz) is one cycle per second. A KHz (Kilohertz) is one thousand cycles per second; a MHz (Megahertz) is one million cycles per second; a GHz (Gigahertz) is one billion cycles per second.
Frequency Response:
The change of gain with frequency.
Front Porch:
That portion of the composite picture signal which lies between the leading edge of the horizontal blanking pulse, and the leading edge of the corresponding sync pulse.
Full Network Station:
A commercial television broadcast station that generally carries 85 per cent of the hours of programming offered by one of the three major national networks during its weekly prime time hours.
Fully Integrated System:
A CATV system designed to take advantage of the optimum amplifier-cable relationship for highest performance at lowest cost. Such a system is also admirably suited to the fully automated CATV system concept.
Gain:
A measure of amplification expressed in dB. For matched CATV components. Gain of an amplifier is usually specified at the highest frequency of operation, for example, at Channel 13 of all-band equipment.
Ghost:
A shadowy or weak image in the received picture, offset either to the left or right of the primary image, the result of transmission conditions which create secondary signals that are received earlier or later than the main or primary signal. A ghost displaced to the left of the primary image is designated as "leading" and one displaced to the right is designated as "following" (lagging). When the tonal variations of the ghost are the same as the primary image, it is designated as "positive" and when it is the reverse, it is designated as "negative."
Government Channel:
FCC rules require cable systems in the top 100 markets to set aside one channel for local government use, to be available without cost for the "developmental period." That period runs for five years from the time that subscriber service began, or until five years after the completion of the basic trunk line.
Grandfathering:
Exempting cable systems from the federal rules because 1) they were in existence or operation before the rules, or 2) substantial investments were made in system construction before the rules. Grandfathering applies to signal carriage, access channels and the certification process.
Group Delay:
Delay of colour components to picture components of signal caused by movement through device which has non-linear frequency response components; i.e., inductors and capacitors.
Halo:
Most commonly, a dark area surrounding an unusually bright object, caused by overloading of the camera tube. Reflection of studio lights from a piece of jewelry, for example, might cause this effect. With certain camera tube operating adjustments, a white area may surround dark objects.
Hardware:
The equipment involved in production, storage, distribution or reception of electronic signals. In CATV it means the headend, the coaxial cable network, amplifiers, the television receiver and production equipment like cameras and videotape recorders.
Harmonic Distortion:
Form of interference involving the generation of harmonics according to the frequency relationship f = nf1 for each frequency present, where n is a whole number equal to 2 or more.
Headend:
Electronic control center -- generally located at the antenna site of a CATV system -- usually including antennas, preamplifiers, frequency converters, demodulators, modulators and other related equipment which amplify, filter and convert incoming broadcast TV signals to cable system channels.
High Band:
TV channels 7 through 13.
High VHF Band:
Part of the frequency band which the FCC allocates to VHF broadcasting, including channels 7 through 13, or 174 through 216 MHz.
Horizontal (Hum) Bars:
Relatively broad horizontal bars, alternately black and white, which extend over the entire picture. They may be stationary, or may move up or down. Sometimes referred to as a "venetian blind" effect. Caused by approximate 60-cycle interfering frequency, or one of its harmonic frequencies.
House Drop:
The coaxial cable that connects each building or home to the nearest feeder line of the cable network.
Hue:
Corresponds to "colour" in everyday use; i.e., red, blue, etc. Black, white and grey do not have hue.
Hum Modulation:
Form of distortion where the power-line frequency modulated the TV signal, causing hum bars to appear in the picture.
Independent:
A TV station that has no exclusive affiliation which obliges it to carry programs from one of the national networks.
Inline Package:
A housing, for amplifiers or other CATV components, designed for use without jumper cables; cable connectors on the ends of the housing are in line with the coaxial cable.
Insertion Loss:
Additional loss in a system when a device such as a directional coupler is inserted; equal to the difference in signal level between input and output of such a device.
Interchangeability:
The ability to exchange tapes between different manufacturers' videotape recorders with no appreciable degradation of playback image.
Interconnect:
To link CATV headends, usually with microwave, so that subscribers to different cable systems can see the same programming simultaneously.
Interference:
Energy which tends to interfere with the reception of the desired signals, such as fading from airline flights, r-f interference from adjacent channels, or "ghosting" from reflecting objects such as mountains and buildings.
Interlaced Scanning (Interlace):
A scanning process in which each adjacent line belongs to the alternate field.
Intermodulation Distortion:
Form of interference involving the generation of interfering beats between two or more carriers according to the frequency relationship f = nf1 ± mf2, where n and m are whole numbers (but not zero), with appropriate expansion for additional carriers.
Jumper Cable:
Short length of flexible coaxial cable used in older CATV systems to connect system coaxial cable to amplifiers or other CATV components; they have no place in a modern, high quality system. The automotive equivalent will be required to restart the hearts of telco Internet project managers when we launch Internet over cable.
Kinescope Recording:
A film recording made by a motion picture camera designed to photograph a television program directly from the front of a television tube. Often called a "kine."
Leapfrogging:
CATV operators' practice of skipping over one or more of the nearest TV stations to bring in a farther signal for more program diversity on the cable. FCC rules establish priority for carrying stations that lie outside the cable system's service area.
Leaseback:
The practice by telephone companies of installing and maintaining CATV distribution systems, and "leasing" the facilities "back" to separate contractors for operation of the system.
Leased Channel:
In addition to the designated channels (education, government and public access) and over-the-air broadcast channels, cable systems must make the remainder of their channels available for lease. At least one channel is to be available for lease by part-time users. Channels can be leased by group or individuals for the sole use of the lessee at posted rates. The operator must not censor or control program content in any way, under FCC rules.
Level Diagram:
A graphic diagram indicating the signal level at any point in the system.
Line Extender or Distribution Amplifier:
Types of amplifiers used in the feeder system.
Line Frequency:
The number of horizontal scans per second, nominally 15,750 times per second.
LDS (Local Distribution System):
A wide band microwave system or cable system which is capable of transporting a number of television signals simultaneously. Used to interconnect cable system headends.
Local Origination Channel:
A channel on a cable system (exclusive of broadcast signals) which is programmed by the cable operator and subject to his exclusive control.
Local Signals:
Television signals that are received at locations that are within the station's Predicted Grade B Contour. Cable systems must carry all commercial local signals in their areas.
Low Band:
TV channels 2 through 6.
Low VHF Band:
The part of the frequency band allocated by the FCC for VHF broadcast television, including television channels 2 through 6, or 54 through 108 MHz.
Luminance Signal:
That portion of the NTSC colour television signal which contains the luminance or brightness information.
Main Trunk:
The major link from the headend to feeder lines.
Microsecond:
One millionth of a second.
Microwave:
Line-of-sight, point-to-point transmission of signals at high frequency. Many CATV systems receive some television signals from a distant antenna location with the antenna and the system connected by microwave relay.
Mid Band:
The part of the frequency band that lies between television channels 6 and 7, received by the FCC for air, maritime and land mobile units, FM radio and aeronautical and maritime navigation. Mid band frequencies, 108 to 174 MHz, can also be used to provide additional channels on cable television systems.
Modulator:
The electronic equipment required to combine video and audio signals from a studio and convert them to radio frequencies (r-f) for distribution on a cable system. Also, a very low-powered television signal generator used to provide signals for distribution on a CATV system.
MSO (Multiple System Operator):
A company which owns more than one CATV system.
N + 1:
A formula which refers to the FCC requirements that provide for expansion of channel capacity for nonbroadcast use. If the governmental, educational, public access and leased channels are in use 80 percent of the weekdays (Monday through Friday) for 80 percent of the time during any three-hour period for six consecutive weeks, the system operator must expand the system's channel capacity within six months.
Net Weekly Circulation (NWC):
The estimated number of television households viewing a particular station at least once per week, Monday-Sunday, 6 a.m. to 2 a.m., EST. Used to determine whether a station is "significantly viewed" in an area and must be carried by a cable system operating in that area.
Network:
Group of radio or television outlets linked by cable or microwave that transmit identical programs simultaneously, or the company that produces programs for them. The three national commercial television networks in the U.S. are the American Broadcasting Company, the Columbia Broadcasting Company and the National Broadcasting Company.
Noise:
The word "noise" is a carryover from audio practice. Refers to random spurts of electrical energy or interference. May produce a "salt-and-pepper" pattern over the picture. Heavy noise sometimes is called "snow."
Noise Figure:
A measure of the noise in dB generated at the input of an amplifier as compared with the noise generated by a 75-ohm resistor.
Off-the-air:
Reception of a TV signal that has been broadcast through the air.
OTP (Office of Telecommunications Policy):
Division of the Executive Office of the President staff that advises the Executive Branch on communications policy, studies policy questions and develops legislative proposals.
Ordinance:
A local law which governs the institution and operation of a cable television system in a community.
Overlapping Markets:
A case where a TV station's Predicted Grade B Contour is overlapped by the Predicted Grade B Contour of a television station located in a different market.
Pairing:
A partial or complete failure of interlace in which the scanning lines of alternate fields do not fall exactly between one another but tend to fall (in pairs) one on top of the other.
Passive Device:
A circuit or network not using active devices such as tubes to transistors.
Pay TV:
A system of television in which scrambled signals are distributed and are unscrambled at the homeowner's set with a decoder that responds upon payment of a fee for each program. Pay TV can also refer to a system where subscribers pay an extra fee for access to a special channel which might offer sports programs, first-run movies or professional training.
CATV Penetration:
The ratio of the number of subscribers to the total number of households passed by the cable system. Penetration is the basis of a system's profitability.
Percentage Sync:
The ratio, expressed as a percentage, of the amplitude of the synchronizing signal to the peak-to-peak amplitude of the picture signal between blanking and reference white level.
Performance Standards:
The minimum technical criteria that must be met by CATV systems, consistent with standard set by the FCC or the local ordinance.
Picture Tube:
A cathode-ray tube used to produce an image by variation of the intensity of a scanning beam.
Pole Attachment:
When CATV systems use existing pole lines maintained by power and telephone companies, an attachment contract must be negotiated between the parties of interest.
Predicted Grade A Contour:
The line representing the service area in which a good picture is computed to be available 90 percent of the time at 70 percent of the receiver locations. Signal contours determine what educational channels are carried on a cable system and, in smaller markets, what stations must be carried from other small markets.
Predicted Grade B Contour:
The concentric area marking a television station's service area in which a good picture is computed to be available 90 percent of the time at 50 percent of the receiver locations.
Program Nonduplication:
Under FCC rules, a cable system must black-out the programming of a distant television station it carries, when the system would duplicate a local station's programming, on the request of the local station.
Public Access:
To ensure that divergent community opinion is aired on cable television, FCC rules require systems in the top 100 markets to set aside one public access channel along with the education and government channels. The public access channel is free and available at all times on a first-come, first-served basis for noncommercial use by the general public.
Public Television:
Noncommercial television broadcasting.
Raster:
The scanned (illuminated) area of the cathode-ray picture tube.
Receiver Isolation:
The attenuation between any two receivers connected to the system.
Reflection Coefficient:
Ratio of reflected wave to incident wave -- mathematically related to VSWR.
Reflections or Echoes:
In video transmission this may refer either to a signal or to the picture produced.
1. Signal:
a) Waves reflected from structures or other objects.b) Waves which are the result of impedance or other irregularities in the transmission medium.
2. Picture:
"Echoes" observed in the picture produced by the reflected waves .
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 three quarters of the width of the picture. This information usually is derived by observation of the vertical wedge of a test pattern. A picture which is sharp and clear and shows small details has good, or high, resolution. If the picture is soft and blurred and small details are indistinct it has poor, or low, resolution. Horizontal resolution depends upon the high-frequency amplitude and phase response of the pickup equipment, the transmission medium and the picture monitor, as well as the size of the scanning spots.
Resolution (Vertical):
The amount of resolvable detail in the vertical direction in a picture. It is usually expressed as the number of distinct horizontal lines, alternately black and white, which can be seen in a test pattern. Vertical resolution is primarily fixed by the number of horizontal scanning lines per frame. Beyond this, vertical resolution depends on the size and shape of the scanning spots of the pickup equipment and picture monitor and does not depend upon the high-frequency response or bandwidth of the transmission medium or picture monitor.
Return Loss:
Reflection coefficient expressed in dB.
R-F Pattern:
A term sometimes applied to describe a find herringbone pattern in a picture. May also cause a slight horizontal displacement of scanning lines resulting in a rough or ragged vertical edge of the picture. Caused by high-frequency interference.
Ringing:
An oscillatory transient occurring in the output of a system as a result of a sudden change in input. Results in close-spaced multiple reflections, particularly noticeable when observing test patterns, equivalent square waves, sine-squared signal, or any fixed objects whose reproduction requires frequency components approximating the cutoff frequency of the system.
Roll-off:
A gradual attenuation of gain-frequency response at either or both ends of the transmission pass band.
Scanning Line:
A single continuous narrow strip of the picture area containing highlights, shadows, and halftones, determined by the process of scanning.
Second Order Beat:
An unwanted carrier created by two separate carriers beating against each other. These beating carriers may have the same or different frequencies.
Second Harmonic:
A second order beat whose two beating carriers have the same frequency.
Semiconductor:
Material with an electrical characteristic which is insulators. Most commonly used semiconductors for transistors and diodes are germanium, silicon, and gallium arsenide.
Signal Level:
The rms voltage measured during the r-f signal peak. It is usually expressed in microvolts referred to an impedance of 75 ohms, or in dBmV, the value in decibels with respect to a reference level of 0 dBmV, which is 1 millivolt across 75 ohms.
Signal-to-noise Ratio:
The ratio of the signal to noise level with both measured either at the input or output of electronic equipment, usually expressed in dB.
Slope:
Difference in amplifier gain, or change in cable attenuation, between lowest and highest frequency present.
Slope-compensation:
The action of a slope-compensated gain control, whereby slope of amplifier equalization is simultaneously changed with the gain so as to provide the correct cable equalization for different lengths of cable; normally specified by range and tolerance.
Smear:
A term used to describe a picture condition in which objects appear to be extended horizontally beyond their normal boundaries in a blurred of "smeared" manner. Also, the kind of campaign waged by telephone companies to counter the wildly successful Internet over cable service.
Snow:
Heavy random noise.
Software:
Programming and programming materials such as films, videotapes and slides.
Solid State:
A term taken from physics, used interchangeably with the word transistorized; also includes other semiconductor elements, such as diodes. Generally refers to tubeless equipment.
Spacing:
Length of cable between amplifiers expressed as dB loss at the highest TV channel provided for in a system, equal to amplifier gain in main trunks.
Span:
Distance between line extenders or distribution amplifiers; also, distance between taps.
Special Effects Generator:
A device permitting combinations of images on a television screen supplied by one or more video inputs.
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.
Sports Blackout:
Federal law requires cable systems and television stations to delete coverage of local sports events to protect gate receipts.
Streaking:
A term used to describe a picture condition in which objects appear to be extended horizontally beyond their normal boundaries. This will be more apparent at vertical edges of objects when there is a large transition from black to white or white to black. The change in luminance is carried beyond the transition, and may be either negative or positive. For example, if the tonal degradation is an opposite shade to the original figure (white following black), the streaking is called negative; however, if the shade is the same as the original figure (white following white), the streaking is called positive. Long streaking may extend to the right edge of the picture and, in extreme cases of low-frequency distortion, can extend over a whole line interval. Also, the favorite field activity of cable engineers.
Sub Band:
The frequency band from 6 MHz to 54 MHz, which may be used for two-way data transmission.
Subscriber:
A person who pays a fee for cable services.
Super Band:
The frequency band from 216 to 600 MHz, used for fixed and mobile radios and additional television channels on a cable system.
SYNC Generator:
A device used to supply a common or master sync signal to a system of several cameras. This ensures that their scanning pulses will be in phase. Scanning pulses out of phase produce distortion or rolling, sometimes called "sync loss."
Switcher:
A control which permits the selection of one image from any of several cameras to be fed into the television display or recording system.
Switcher/Fader:
A device permitting gradual, overlapping transition from the image of one camera to another. Sometimes incorporated as part of a special effects generator.
Switched Service:
A cable communications service in which each subscriber has a terminal and may communicate with any other subscriber.
Sync:
An abbreviation for the words "synchronization," "synchronizing," etc. Applies to the synchronization signals, or timing pulses, which lock the electron beam of the picture monitors in step, both horizontally and vertically, with the electron beam of the pickup tube. The colour sync signal (NTSC) is know as the colour burst.
Sync Compression:
The reduction in the amplitude of the sync signal, with respect to the picture signal, occurring between two points of a circuit.
Sync Level:
The level of the tips of the synchronizing pulses.
Synchronization:
Maintenance of simultaneous audio and video signals so that sound and picture operate in phase. Abbreviated "sync."
System Level:
The level of signal in a CATV system at the output of each amplifier. Must be carefully chosen and maintained for least distortion and noise.
System Noise:
Refers to the random energy generated by thermal and shot effects in the system. It is specified in terms of it rms level as measures in a 4 MHz bandwidth centred within a 6 MHz cable television channel.
Tap:
A device installed in the feeder cable which connects the home TV set to the cable network. Also called a drop.
Tariff:
A schedule of services and rates filed by common carriers with regulatory bodies.
Tearing:
A term used to describe a picture condition in which groups of horizontal lines are displaced in an irregular manner. Caused by lack of horizontal synchronization.
Television Households:
A television household is a household having one or more television sets. Estimates for each county are based on an updating of ARB (American Research Bureau) TV penetration estimates. The number of households that watch television in any locality during prime-time hours determines the top 100 markets for FCC cable rules.
Television Market:
A city or complex of closely associated cities served by commercial television broadcast signals from one or more TV stations located within the area. The FCC uses television markets for designating what kind of cable services an operator should provide in terms of signal carriage and nonbroadcast channel use.
TV Penetration:
The percentage of homes having one or more television sets at the time of the ARB American Research Bureau survey. The ARB surveys local markets from October through July; the number of surveys in a year depends on the size of the market.
Terminal:
The connectors, transformers and converter (if necessary) on the cable subscriber's set.
Terminator:
A resistive load for an open coaxial line to eliminate reflections; usually capacitively coupled to avoid shorts in cable-powered systems.
Third Order Beat:
An unwanted carrier created by three separate carriers beating against each other. These beating carriers may have the same or different frequencies.
Third Harmonic:
A third order beat whose three beating carriers all have the same frequency.
Top 100 Market:
Ranking of largest television broadcast areas by size of market; i.e., number of viewers and TV households. Used in FCC rulemakings and in selling of air time to advertisers.
Translator:
A type of relay system which picks up signals from distant or blocked-out television stations, converts the signals to another channel to avoid interference and retransmits them into areas the original signals could not have reached. Translators do not use cable to reach subscribers' homes and do not offer the other kinds of services that cable can provide (local origination, two-way operation, etc.).
Triple Beat:
A third order beat whose three beating carriers all have different frequencies, but are spaced at equal frequency separations.
Trunk Line:
The major distribution cable used in CATV. It divides into feeder lines which are tapped for service to subscribers.
Two-Way Capacity:
A CATV system with two-way capacity can conduct signals to the headend as well as away from it. Two-way or bi-directional systems now carry data; they may eventually carry full audio and video television signals in either direction.
Upstream:
Signals travelling from subscribers to the headend.
UHF:
Ultra High Frequencies, the range of frequencies extending from 300 to 3,000 MHz; also, television channels 14 through 83.
VHF:
Very High Frequencies, the range of frequencies extending from 30 to 300 MHz; also, television channels 2 through 13.
Velocity of Propagation:
Velocity of signal transmission. In free space, electromagnetic waves travel with the speed of light. In coaxial cables, this speed is reduced. Commonly expressed as percentage of the speed in free space.
Vestigial Sideband Transmission:
A system of transmission wherein the sideband on one side of the carrier is transmitted only in part.
Video:
The visual components of a television signal.
Video Band:
The frequency band utilized to transmit a composite video signal.
Videotape:
Used to electronically record sight and sound for instant playback. Videotape comes in half-inch, three-quarters, one and two-inch widths and can be erased and re-recorded.
Video Transmission:
The original video signal before it is modulated and converted to radio-frequency and broadcast or cablecast. A home television set reconverts radio-frequencies to a video signal.
VSWR:
Abbreviation for Voltage Standing Wave Ratio. Reflections present in a cable due to mismatch (faulty termination) combine with the original signal to produce voltage peaks and dips by addition and subtraction. The ratio of the peak-to-dip voltage is termed VSWR. A perfect match with zero reflections produces a VSWR of 1.
VTR:
Abbreviation for videotape recorder, a device which allows the recording and playback of magnetic tape sound and picture recordings.
Windshield Wiper Effect:
Onset of overload in multichannel CATV systems caused by cross-modulation, where the horizontal sync pulses of one or more TV channels are superimposed on the desired channel carrier. Both black and white windshield wiping are observed and are caused by different mechanisms. See also countermodulation.
"Wired City":
The concept of television and other communications data, educational material, instructional television and information retrieval service that wired services can provide. Broadcast services must, of necessity, be limited by scarce spectrum space; wired services have theoretically unlimited channel capacity.