magnetic recording
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What is magnetic recording?
Magnetic recording is a way of preserving sounds, images, and data as electrical signals by selectively magnetizing a magnetic material. A recording head imprints a magnetic signal onto a moving tape or disk. When the recorded tape or disk moves past the playback head, it induces a signal equivalent to the recorded signal.
Magnetic recording has many applications:
* It can be used to store spoken messages in office dictating machines.
* It is used for "instant replay" in live television broadcasts.
* It is used as a telephone answering device.
* It is used to record measurements from laboratory instruments and detection devices.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does magnetic recording work?
Magnetic recording preserves sound, images, and data as electrical signals by selectively magnetizing a magnetic material. A recording head imprints a magnetic signal onto a tape's surface as it passes by. When the recorded tape moves past the playback head, it induces a signal equivalent to the recorded signal, which is then amplified.
Magnetic disks, coated with iron oxide, are also used, with signals recorded as magnetic patterns in spiral tracks. Magnetic disk devices offer advantages over tape recorders because they can directly access specific segments without sequentially passing over content, reducing retrieval time.
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What devices use magnetic recording to store information?
Magnetic recording is used in various devices to store information, including magnetic tape and disk recorders for audio, video, and computer data. Magnetic disks, either hard or floppy, store data as magnetic patterns. Magnetic tape is used in telephone answering devices, and videotape recorders record TV broadcasts. Additionally, magnetic stripes on cards store personal information.
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How does a magnetic tape record and play back sound or data?
A tape recorder uses electromagnetic phenomena to record and reproduce sound waves. The tape consists of a plastic backing coated with a thin layer of tiny magnetic powder.
During recording, a microphone converts sound waves into an electrical signal. This signal creates a time-varying magnetic field in the recording head, magnetizing the powder on the tape to record the wave's shape. The frequency of the signal determines the distance along the tape, and the amplitude determines the extent of magnetization.
During playback, the magnetized tape is drawn past the playback head, where the magnetic imprint on the tape induces a signal equivalent to the recorded signal. This signal is then amplified and converted back into sound waves via a loudspeaker.
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What materials are commonly used in magnetic recording media?
Magnetic recording media commonly utilize materials with specific magnetic properties to preserve sounds, images, and data as electrical signals. The most prevalent material is a coating of fine particles of iron oxide on a plastic ribbon, forming magnetic tape.
For magnetic disk devices, a flat circular plate of metal or plastic is coated on both sides with iron oxide. Other materials with high permeability and remanent magnetization are also suitable, provided they can be readily magnetized and erased without difficulty.
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How has magnetic recording technology changed over time?
Magnetic recording, demonstrated by Valdemar Poulsen in 1900, preserves sound, images, and data as electrical signals through the selective magnetization of magnetic material.
Early magnetic recording devices utilized steel wire. Later, magnetic tape and disks became principal mediums for audio, video, and data storage. Magnetic tape was introduced as a data-storage medium in 1951 in the UNIVAC I computer. Magnetic disks applied to data storage in 1962 offered random accessibility, advantageous over tape recorders.
The development of smaller, flexible floppy disks occurred during the 1970s. By the 1960s, magnetic disk and drum memories began to replace tape units in large systems. Advancements include multiple-track recording and Dolby noise reduction.
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magnetic recording, method of preserving sounds, pictures, and data in the form of electrical signals through the selective magnetization of portions of a magnetic material. The principle of magnetic recording was first demonstrated by the Danish engineer Valdemar Poulsen in 1900, when he introduced a machine called the telegraphone that recorded speech magnetically on steel wire.
In the years following Poulsen’s invention, devices using a wide variety of magnetic recording mediums have been developed by researchers in Germany, Great Britain, and the United States. Principal among them are magnetic tape and disk recorders, which are used not only to reproduce audio and video signals but also to store computer data and measurements from instruments employed in scientific and medical research. Other significant magnetic recording devices include magnetic drum, core, and bubble units designed specifically to provide auxiliary data storage for computer systems.
Magnetic tape devices. Magnetic tape provides a compact, economical means of preserving and reproducing varied forms of information. Recordings on tape can be played back immediately and are easily erased, permitting the tape to be reused many times without a loss in quality of recording. For these reasons, tape is the most widely used of the various magnetic recording mediums. It consists of a narrow plastic ribbon coated with fine particles of iron oxide or other readily magnetizable material. In recording on tape, an electrical signal passes through a recording head as the tape is drawn past, leaving a magnetic imprint on the tape’s surface. When the recorded tape is drawn past the playback or reproducing head, a signal is induced that is the equivalent of the recorded signal. This signal is amplified to the intensity appropriate to the output equipment.
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Tape speeds for sound recording vary from less than 2 inches (5 centimetres) per second to as much as 15 in. (37.5 cm) per second. Video signals occupy a much wider bandwidth than do audio signals and require a much higher relative speed between the tape and the head. Data recording requires even greater speeds. The tape transport of a data-storage unit of a high-performance digital computer, for example, must be able to move the tape past the head at a rate of 200 in. (500 cm) per second.
Magnetic tape was initially designed for sound recording. German engineers developed an audio tape recording machine called the magnetophone during World War II. U.S. and British researchers adopted the basic design of this device to create a magnetic tape recorder capable of high-quality sound reproduction in the late 1940s. Within a decade magnetic tape supplanted phonograph records for radio music programming. Prerecorded tapes in the form of cartridges and cassettes for sound systems in homes and automobiles were in widespread use by the late 1960s.
Related to the audio cassette recorder is a magnetic tape recording system that serves as a telephone answering device. Messages or instructions prerecorded on tape are reproduced automatically when a telephone user’s number is dialed. The answering device then actuates the recording head, which records any messages that the caller wishes to leave.
In 1956 Charles P. Ginsburg and Ray Dolby of Ampex Corporation, a U.S. electronics firm, developed the first practical videotape recorder. Their machine revolutionized television broadcasting; recorded shows virtually replaced live telecasts with a few exceptions, such as coverage of sports events. Almost all programs are videotaped during their original telecasts, and individual broadcasters then rerun the shows at times most suitable for their own viewers. An increasing number of videotape recorders are used for recording television broadcasts received in private homes. Many such units can produce home movies if connected to an accessory video camera. Commercially produced video cassettes of popular motion pictures also can be played on these recorders. See also videotape recorder.
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Magnetic tape was introduced as a data-storage medium in 1951, when it was used in the auxiliary memory of UNIVAC I, the first digital computer produced for commercial use. For about the next 10 years nearly all computers employed magnetic tape storage units. By the 1960s, however, magnetic disk and magnetic drum auxiliary memories began replacing the tape units in large-scale scientific and business data-processing systems that require extremely fast retrieval of stored information and programs. Magnetic tape devices, particularly those using cassettes, continue to be employed as a principal form of auxiliary memory in general-purpose minicomputers and microcomputers because of their low cost and great storage capacity. About 48,000 bits of information can be stored on one inch of tape.
Magnetic tape recorders have also been widely used to record measurements directly from laboratory instruments and detection devices carried aboard planetary probes. The readings are converted into electrical signals and recorded on tape, which can be played back by researchers for detailed analysis and comparison.