Recording head
Encyclopedia
A recording head is the physical interface
between a recording
apparatus
and a moving
recording medium. Recording heads are generally classified according to the physical
principle that allows them to impress their data
upon their medium. A recording head is often mechanically paired with a playback head, which, though proximal to, is often discrete from the record head.
The two most common forms of recording head are:
Note that Magneto-optical recording, though using optics and heat
, should properly be considered a magnetic process, since the data stored on magneto-optical media is stored magnetically.
Earlier systems, such as phonograph
records, used mechanical heads known as styli
to physically cut grooves in the recording medium, in a configuration (of size, width, depth and position) recoverable as sound
.
Electrical connector
An electrical connector is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or...
between a recording
Recording
Recording is the process of capturing data or translating information to a recording format stored on some storage medium, which is often referred to as a record or, if an auditory medium, a recording....
apparatus
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...
and a moving
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
recording medium. Recording heads are generally classified according to the physical
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
principle that allows them to impress their data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
upon their medium. A recording head is often mechanically paired with a playback head, which, though proximal to, is often discrete from the record head.
The two most common forms of recording head are:
- Magnetic - Magnetic recording heads use the principles of electromagnetismElectromagnetismElectromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
to coerceCoercivityIn materials science, the coercivity, also called the coercive field or coercive force, of a ferromagnetic material is the intensity of the applied magnetic field required to reduce the magnetization of that material to zero after the magnetization of the sample has been driven to saturation...
a paramagnetic recording medium, such as ironIronIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
oxides, to orient in a readable manner such as magnetic tapeMagnetic tapeMagnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
. Record heads are constructed of laminated permalloyPermalloyPermalloy is a nickel-iron magnetic alloy, with about 20% iron and 80% nickel content. It is notable for its very high magnetic permeability, which makes it useful as a magnetic core material in electrical and electronic equipment, and also in magnetic shielding to block magnetic fields...
, ferriteFerrite (magnet)Ferrites are chemical compounds consisting of ceramic materials with iron oxide as their principal component. Many of them are magnetic materials and they are used to make permanent magnets, ferrite cores for transformers, and in various other applications.Many ferrites are spinels with the...
, or sendustSendustSendust is a magnetic metal powder that was invented at Tohoku Imperial University in Sendai, Japan, about 1936 as an alternative to permalloy in inductor applications for telephone networks. Sendust composition is typically 85% iron, 9% silicon and 6% aluminum. The powder is sintered into cores...
. As of 2006 this is by far the most dominant type of head in use.
- Optical - Optical recording heads use the principles of opticsOpticsOptics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
and lightLightLight or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
to impart energyEnergyIn physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
on a recording medium, which accepts the energyEnergyIn physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
in a readable manner, e.g. by meltingMeltingMelting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid...
or photographyPhotographyPhotography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
.
Note that Magneto-optical recording, though using optics and heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
, should properly be considered a magnetic process, since the data stored on magneto-optical media is stored magnetically.
Earlier systems, such as phonograph
Phonograph
The phonograph record player, or gramophone is a device introduced in 1877 that has had continued common use for reproducing sound recordings, although when first developed, the phonograph was used to both record and reproduce sounds...
records, used mechanical heads known as styli
Stylus
A stylus is a writing utensil, or a small tool for some other form of marking or shaping, for example in pottery. The word is also used for a computer accessory . It usually refers to a narrow elongated staff, similar to a modern ballpoint pen. Many styli are heavily curved to be held more easily...
to physically cut grooves in the recording medium, in a configuration (of size, width, depth and position) recoverable as sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
.
See also
- Analog recordingAnalog recordingAnalog recording is a technique used for the recording of analog signals which among many possibilities include audio frequency, analog audio and analog video information for later playback.Analog recording methods store signals as a continual wave in or on the media...
- Cassette demagnetizerCassette demagnetizerA cassette demagnetizer is a device that removes the magnetic field that is built up from the use of audio cassettes in a cassette deck.Over time, the passage of magnetically charged cassette tape over the metallic parts of the tape deck will impart a magnetic polarity that can impair the ability...
- Compact CassetteCompact CassetteThe Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a magnetic tape sound recording format. It was designed originally for dictation, but improvements in fidelity led the Compact Cassette to supplant the Stereo 8-track cartridge and reel-to-reel...
- Digital recordingDigital recordingIn digital recording, digital audio and digital video is directly recorded to a storage device as a stream of discrete numbers, representing the changes in air pressure for audio and chroma and luminance values for video through time, thus making an abstract template for the original sound or...
- Sound recording and reproductionSound recording and reproductionSound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...
- VCR
- VideotapeVideotapeA videotape is a recording of images and sounds on to magnetic tape as opposed to film stock or random access digital media. Videotapes are also used for storing scientific or medical data, such as the data produced by an electrocardiogram...
- Video head cleanerVideo head cleanerA video head cleaner is a substance used for cleaning the record/playback heads of a video or audio cassette player.Audio and video cassette players require regular maintenance to perform properly. Particles that come off the magnetic tape from the videocassette can build up on the helical scan...
- VTR
External links
- Diagrams and explanations of recording heads and the tape recording process.
- An Ampex recording head, deconstructed.
- A tape recorder, showing the head assemblies.
- Photo of an early recording head as part of a wire recorder.
