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GLOSSARY

A/C Head
Audio / Control Head. A combined unit which reads/writes both the linear sound track and the control (sync) pulses.
Aerial
The antenna which picks up a radio or TV transmission. Also, the coax lead from the antenna which you plug into the back of a VCR or TV set.
Analogue
A signal which is represented by some physical quantity whose values are an analogue, or copy, of the signal value being represented. For example, the signal generated by a microphone is an electrical voltage, and if the loudness doubles so does the voltage. Similarly, a clock with hands is called analogue because the angular position of a hand is an analogue of the time it represents. Compare digital.
AM
Amplitude Modulation.
Amplitude Modulation
Representing a signal as a change in the amplitude (strength, or level) of a fixed-frequency carrier.
Audio Dub
A special recording mode where the video signal on the tape is left unchanged, but new sound is recorded.
Audio Head
The head which records / reads the sound information.
Audio / Control Head
A head which reads both the sound information, and the other control and synchronisation information. Many VCRs use a single or combined head for both.
AV
Audio / Video. Baseband signals. Compare RF.
Azimuth
The angle of a read/write head, relative to the direction of writing. 0 degrees azimuth means it is "square on".
Badge Engineering
The practice of changing the badge and sometimes other minor cosmetics in order to make a machine from one manufacturer look as if it was produced by another.
Bandwidth
The range of frequencies required by a signal. Standard video requires a bandwidth of 5.5 MHz
Baseband
Raw signals which have not been modulated or mixed with any other carrier or signal.
Betamax
Sony's domestic 1/2 inch format, introduced in 1975 (Japan and US) / 1978 (UK and Europe). The "beta" comes from the Japanese word for quality, so Betamax means Highest Quality.
Broadcast
A transmission aimed at multiple receivers, such as public TV and radio. The opposite is Narrowcasting, which means transmitting to one particular reciever (or small group of recievers).
Broadcast Quality
Video of high enough quality to be used for broadcast TV. A resolution of at least 500 lines is required, though modern high-band consumer equipment (eg SVHS, Hi8, DV) is good enough to be used where a full-sized camcorder would be impractical.
Capacitance
An electronic property. The amount of electrical charge a device can hold.
Capstan
A rotating shaft which pulls the tape through the recording mechanism at a constant speed.
Cartridge
A case containing a single spool of tape. The tape is wound out of the case onto another spool within the machine, or is an endless loop. Compare cassette.
Carriage
The mechanism which holds the cassette and allows it to be inserted or removed from the tape mechanism.
Carrier
The high-frequency signal onto which an actual information signal is modulated.
Cassette
A case containing both spools of tape, which allows them to be handled easily. Compare cartridge.
CAV
Constant Angular Velocity. Playing a disc at a fixed RPM, which means that the track will pass the pickup at a higher linear speed when the pickup is at the edge than nearer the centre. Compare CLV.
CD
The now-ubiquitous 12cm digital audio disc format, also used for computer data, video, photographs etc.
Channel
One particular TV program out of all those being broadcast at once.
Chassis
The metal framework on which all of a VCR's tape transport components are mounted.
Chip
See Integrated Circuit.
Chrominance
The colour information in a video signal. Compare Luminance.
C-Lacing
The lacing system used by VCR, Betamax and U-Matic recorders, where the tape is pulled out and around the drum from one side, forming a C shape. Compare M-Lacing.
Clone
A machine which is built by one company but badge engineered and otherwise reworked to make it appear to be a different machine from a different manufacturer.
CLV
Constant Linear Velocity. Playing a disc so that the track passes the pickup at a fixed linear speed, which means spinning the disc more slowly when the pickup is at the edge than nearer the centre. Compare CAV.
Coherent
All together. In laser light, coherent means that the light waves are all in step: they have the same frequency and phase.
Colour Under
A technique used in most video systems to record colour without requiring the full bandwidth of a normal signal. The chrominance is heterodyned with a reference signal, to produce a low-frequency "difference" signal, and this is then modulated onto the luminance signal.
Cross Colour
A video system of limited bandwidth can confuse the highest luminance frequencies with chrominance information. The effect is flickering colours, often seen on tweed jackets and other fine-patterned clothing.
Cue / Review
The ability to fast-forward or rewind a video tape, while still seeing the (speeded up) picture on the TV.
CVC
Compact Video Cassette. A 1/4 inch portable video format from Technicolor / Funai, introduced in 1980.
Digital
A signal which is processed as binary (base 2) numbers, represented by some physical quantity which only takes two values. So, the binary number 011010 might be represented by a sequence of voltage pulses (off,on,on,off,on,off); doubling this value (to 110100) changes the sequence of voltages but not their actual values. Compare analogue.
Discrete
In electronics, discrete means using individual components like transistors, capacitors etc, rather than integrated circuits ("chips").
DTF
Dynamic Track Following. A system which uses a moveable video head to accurately scan a track.
Dubbing
The process of copying a recording from one tape onto another.
Erase Head
The head which erases information from the tape.
Event
A recording programmed into a timer.
Field
Half a frame, consisting of alternate lines - eg all the odd ones or all the even ones.
FM
Frequency Modulation.
Format
The combination of dimensions, speeds and electronic specifications which defines a particular cassette recording system.For example, VHS and Betamax are both formats.
Frame
A single still image from a TV signal. Standard TV runs at 25 frames per second (30 in US/Japan). Compare Field.
Frames Per Second
The refresh rate of a TV signal. See frame.
Frame Rate
The number of Frames Per Second of a TV picture.
Frequency Modulation
Representing a signal as the change in frequency of a carrier.
Frontloader
A VCR where the cassette is inserted into a slot in the front of the machine. Compare Toploader.
Gas Discharge
A display technology similar to neon or fluorescent tubes, which produces bright displays but uses a lot of power.
Guard Bands
Gaps between tracks, necessary to prevent a head picking up signals from adjacent tracks it reads its own track.
Head
A device which reads and / or writes information from / to a magnetic tape.
Head Drum
A spinning cylinder which holds the read/write heads on a helical scanning video machine.The drum guides the tape so that the heads can stay in contact with it as they spin past.
Helical Scanning
The normal method of recording video, where the read/write heads are moved across the tape at high speed by spinning them on the head drum, while the tape is moved slowly past the drum.
Heterodyning
A high-frequency signal can be converted into a low-frequency signal by "subtracting" a reference signal of a known, fixed frequency which is near that of the original. The result is a difference signal which, by adding back a reference signal, can be used to recreate the original one.
HiFi
High Fidelity. An audio system which can reproduce frequencies from 200Hz to about 20,000Hz.
High Band
Some video formats come in two varieties: low band and high band. A high-band machine gives better performance, using higher bandwidth and signal separation etc; a low-band machine is cheaper but performs less well.
Holography
The technology of storing information using the patterns generated by interfering lasers. Can be used to create holograms, true 3D pictures, or to store non-visual information.
Hz
Hertz. The unit of frequency; 1Hz is one cycle per second.
I.C.
Integrated Circuit
Incandescent
So hot that it's glowing. Of bulbs, means a normal filament bulb, as opposed to a fluorescent, neon or LED.
Infra-red
Light which is of a longer wavelength (redder) than the longest which we can see. Commonly used for remote controls.
Integrated Circuit
A device containing many electronic components on a tiny sliver of silicon. More commonly known as a silicon chip.
Interference
The unwanted effect of an electrical circuit on the others nearby. A badly shielded car ignition can cause sparks and buzzing on a TV set; this is interference.
Interlacing
The technique of scanning a TV frame as two fields, each field comprising all the odd-numbered lines in the frame or all the even lines.
Lacing
The process of wrapping the tape around the head drum and other heads / guides in a video machine. All home VCRs lace up automatically; early VTRs required manual lacing.
Laser
Light Amplification by Stimulated Emmission of Radiation. A device which produces a very tight beam of pure, monochromatic coherant light.
LCD
See Liquid Crystal Display.
LED
Light Emmitting Diode. An electronic "bulb" which produces coloured light without the heat of a normal bulb, and which uses less power and never burns out.
Line
A single line of a TV picture. Standard TV has 625 lines in a frame (525 in US/Japan)
Linear
In a line. In the video sense, a linear recording is one where the head-to-tape motion is entirely that of the tape itself - the heads remain stationary. Compare with Helical Scanning.
Liquid Crystal Display
A display technology which uses a fluid with optical properties which change when an electric field is applied, to alter the polarisation of light passing through it. LC displays take almost no power, but unlike LED or Gas Discharge displays do not themselves generate light.
Logic Control
An intelligent operator interface, which only performs the requested action if it makes sense (eg it will ignore the rewind button if the VCR is recording), and which sometimes allows button presses to be "stacked up" so that they will be executed when the machine has finished doing what it is currently busy with.
Long Play
A technique to increase the record/playback time of a format by slowing the tape down. This usually reduces the picture quality, though this can be compensated for using separate heads for SP and LP, and picture enhancing circuitry.
LP
Long Play.
Low Band
Some video formats come in two varieties: low band and high band. A high-band machine gives better performance, using higher bandwidth and signal separation etc; a low-band machine is cheaper but performs less well.
Luminance
The brightness information in a video signal. Compare chrominance.
Mains
The household electricity supply - 240V 50Hz in the UK, 110V 60Hz in the USA.
Micron
A millionth of a metre; a thousandth of a millimetre.
Microprocessor
A "computer on a chip" - an electronic device which can execute a stored program.
M-Lacing
A lacing pattern used by V2000 and VHS machines, where the tape is pulled out by two fingers, one each side of the head drum, forming an M shape with the drum in the middle. Compare C-Lacing.
Modulation
The process of impressing one signal (the information) onto another (the carrier).
Modulator
A device which allows a VCR to be connected directly to a TV set. It converts a baseband video signal into an RF (aerial) signal.
Monitor
A TV set without a tuner. Used to display baseband video.
Monochrome, Monochromatic
Single coloured. For TVs / VCRs, refers to black and white systems.
Monophonic
Single channel sound, as opposed to Stereo.
NiCad
Nickel Cadmium. The most common rechargeable battery technology.
Noise
Interference, particularly hissing on audio or snow on video.
Noise Bars
The bands of 'snow' across a picture during pause or fast-forward/rewind.These are caused by the heads crossing from one track to another, since the tape is not moving at its usual speed so the heads can't track properly.
NTSC
National Television Standards Committee. The colour TV system used in North America and elsewhere.
Optical
Dealing with light.
PAL
Phase Alternating Line. The colour TV format used in the UK, Australia and elsewhere.
Pause-Record
The ability to engage Pause and Record at the same time, so that recording will start as soon as pause is released. This is not only faster (since the machine is already laced) but usually produces cleaner starts to recordings.
PCM
Pulse Code Modulation. A digital audio recording format.
Piano Key
A style of operating control where the main function buttons are large, protruding paddles resembling piano keys. Usually used by wholly mechanical systems as they have a large throw and therefore a large mechanical movement.
Pickup
The part of any system which reads the signal from the medium. For example, the read head on a tape recorder, or the stylus on a record player.
Picture Search
See Cue / Review
Piezo-electric crystal
A crystal which generates an electric current if forced to change shape (by squeezing or stretching), and changes shape if an electric current is applied to it.
Pinch Roller
A rubber roller which presses the tape tightly against the capstan.
Portapak
A term used to refer to the portable reel-to-reel VTRs in the 60s.
Power Supply
The unit that allows a portable / separates VCR to be connected to the mains.
Preset
A small variable resistor commonly used as a tuning knob in older TV and VCR tuners. The preset tunes in one particular button on the tuner's channel selector - that button is then pre-set to that channel.
Program
In the video sense, the information needed to drive a timer: the start time, stop time and channel to be recorded etc.
PVC
Poly Vinyl Chloride. A type of plastic.
Quad
See Quadruplex.
Quadrophonic
An obsolete music system from the 70's which used 4 speakers (as opposed to stereo, with 2).
Quadruplex
The first successful video recording system, introduced by Ampex in 1956. Quad used a vertical scanning system, with the read/write heads mounted on a spinning disc to scan the 2-inch tape across its width.
Read/Write Head
A head which is used to record and play back information on a tape.
Recording Density
The area of magnetic surface (on a tape or disc) required by a particular format to record a particular signal.
Reel To Reel
A tape machine which uses naked spools, as opposed to cassettes or cartridges.
Review
See Cue / Review
RF
Radio Frequency. The signal picked up by a TV aerial. RF signals include the video and audio, modulated onto a UHF carrier.
Scanning (1)
The process of moving a head along a recorded track on a magnetic tape or disc.
Scanning (2)
The process of moving an electron beam back and forth to display a TV picture.
Search and Store
A tuning system where the machine scans the waveband and stops whenever it finds a strong signal. This can then be assigned to one of the tuner's channel buttons.
SECAM
Sequentiel Coleur avec Memoire. The colour TV system used in France, the Middle East and elsewhere.
Servo
An electronic circuit which controls the speed of a mechanism, measuring the actual speed and adjusting the control signals as required to change to the desired speed.
Sessile
Fixed in place, like a limpet or a plant. The opposite of mobile.
Slant-Azimuth
A technique to prevent a head accidentally picking up signals from an adjacent track. The two heads are mounted at opposite angles (relative to the direction of writing), so that the signal strength from an accidentally read adjacent track is much reduced - only recordings made by a head at the same angle will give a strong signal.
Snow
In the TV / Video sense, the noise seen on a TV screen when there is no signal.
Solenoid
An electromechanical device which produces a linear motion (push or pull) when power is applied.
Solid State
An electronic device with no moving parts or evacuated/gas filled glass envolopes. Solid State devices consist of circuitry etched onto fragments of silicon or another semiconductor.
SP
Short Play, Standard Play. The opposite of Long Play
Spool (1)
The reel or bobbin on which tape is wound. In a modern cassette machine, the spools are inside the cassettes.
Spool (2)
To fast-forward or rewind.
Still Frame
The ability to pause the tape and leave a freeze-frame picture on the screen.
SVR
Super Video Recording. Grundig's domestic tape format, developed from VCR / VCR-LP in 1979.
Tape Guides
The pins, wheels and rollers which guide the tape around the various heads in the recorder.
Tape Transport
The mechanism responsible for moving the tape, during play/record, fast forward, rewind etc.
Test Signal
A signal generated by a VCR in order to have something to tune the TV set into when setting up the machine. Typically this will be a pattern of black and white lines, sometimes with an audio tone as well.
Time Coding
Recording extra information on a tape so that an editing system can identify the exact point on the recording, usually down to the exact frame.
Timer
A device which allows a VCR to be programmed, so that it can record one or more programs while unattended.
Toploader
A VCR where the cassette carriage raises out of the top of the machine. Compare Frontloader.
Track
The area of a magnetic tape where the actual recorded signal is. In helical scanning machines, the tracks are recorded diagonally across the width of the tape, like this: //////////////.
Tracking
Adjusting a VCR or VTR so that its heads accurately scan the tracks on the tape.
Trick Play
Any playback function other than the basic normal-speed play: cue/review, still frame, reverse play etc.
TTU
Tuner / Timer Unit. That part of a separates system containing the tuner, timer and often power supply and battery charger. The unit that is NOT required when out shooting.
Tube
The glass display screen of a TV, or more generally any thermionic device ("valve").
Tuner
A device which allows a TV or VCR to pick up broadcast signals using an aerial, and one particular station to be selected from all those available. It converts the recieved RF signal to a baseband video signal.
U-Matic
Sony's proffessional/industrial 3/4 inch format, available in two versions: low band and high band.
Unlacing
The opposite of lacing; removing the tape from the tape mechanism and returning it to the cassette.
VCC
Video Compact Cassette. An obsolete name for the Video 2000 format.
VCR (1)
Video Cassette Recorder. In the virtual museum, the term VCR always means a normal, domestic video machine.
VCR (2)
Video Cassette Recording. The first true domestic video format, introduced by Philips in late 1972.
VCR-LP
A long-play version of Philips original VCR video format, introduced in 1978.
VHS
Video Home System. JVC's domestic 1/2 inch format, introduced in 1976 (Japan and US) / 1978 (UK and Europe).
VHS-C
Compact VHS. A miniature version of VHS, which uses the same tape and recording format but smaller cassettes.
Videographer
An obsolete term for someone who makes/shoots videos.
Video 2000
See V2000.
Video8
A miniature format using 8mm tape, designed by Sony and a consortium of others and introduced in 1985.
VTR
Video Tape Recorder. In the virtual museum, this term means a video recorder which does not have a tuner, timer and / or modulator, so would not be suitable for home use.
V2000
Video 2000. Philips domestic 1/2 inch format (which allowed the tapes to be turned over, so was really a 1/4 inch format). Developed from VCR / VCR-LP, V2000 was introduced in 1980.
8-Track
An obsolete audio cartridge system, popular in the 70's. 8-Track cartridges used an endless loop of tape.
16mm
A mid-range cine film gauge, higher quality than standard 8 or super 8, but not cinema quality.