Videotape recorder is a device that records visual images and sound on magnetic tape. Videotape recorders, also known as VTR’s or simply video recorders, also play back the recorded video (picture) and audio (sound) information on television sets or other display devices.
Videotape recorders were first used by the television broadcasting industry during the 1950’s. They became essential equipment to record and replay commercials, regular TV series, and many other telecasts. VTR’s allowed programmers to plan and organize TV schedules. They also enabled broadcasters to show reruns of programs and to replay commercials.
Videotape has a number of advantages over motion-picture photographic film. For example, videotape can be played back immediately after being recorded on, but film must be developed before it can be viewed. For this reason, camera operators who use videotape can determine right away whether a scene needs to be re-recorded. In addition, videotape can be erased and recorded over, but film cannot.
Today, VTR’s have been largely replaced by digital video recording formats. However, VTR’s continue to be used for archival storage due to their low cost.
Types of videotape recorders
In addition to the professional models used by TV broadcasters, several other types of VTR’s were once common. Some schools and businesses used semiprofessional videotape recorders to record educational programs and employee training films. From the mid-1980’s to the early 2000’s, many consumers recorded TV programs and played back prerecorded cassettes of movies on home videotape recorders, also called videocassette recorders (VCR’s). The various types of video recorders differed in the size of the tape they used and the quality of the images they produced. Most types were designed to use tape cassettes.
People commonly use portable camcorders to make home movies. Until the early 2000’s, many of these devices combined a camera and a VTR in a single unit powered by batteries. The camera and a microphone sent video and audio signals to the recorder. Today, most camcorders record digital video files instead of using tape. See Camcorder.
How videotape recorders work
Videotape consists of a long plastic strip coated with particles of magnetic material. Videotape recorders record television signals by translating them into magnetic fields. These fields create patterns of magnetization in the coating. The process is reversed during playback, when the magnetic patterns are translated into television signals for viewing on TV sets. For information about where television signals come from and how they are made into a TV picture, see Television (Home entertainment systems).
Videotape recorders store visual images and sound as either (1) analog signals or (2) digital signals. In an analog recording, the magnetic patterns are analogous (similar) to those of the original television signals. In a digital recording, the recorder translates the television signals into a numerical code. Digital recording produces better picture and sound quality than analog recording does. Many professional videotape recorders and many camcorders use digital technology.
Recording.
The recorder converts the TV signal into electric current, which travels through wire coils of small electromagnets called heads. A head is a ring of metal that has a narrow cut called a gap. Opposite the gap, a coil of wire is wrapped around the ring. This coil conducts the current corresponding to the TV signal. The current produces a strong magnetic field in the ring and in the gap. When videotape passes over the gap, the field creates the patterns of magnetization. The patterns remain until they are recorded over or they are removed by an erase head, which demagnetizes the tape.
The patterns recorded on many types of analog videotape consist of three types of tracks (lines of magnetized particles): (1) video tracks, (2) audio tracks, and (3) control tracks.
Video tracks contain signals that represent visual images. The tracks are recorded helically (diagonally) and take up most of the tape. Video tracks are recorded by video heads mounted on a rotating metal cylinder called a drum. The heads scan (pass over) the tape at high speed while recording or playing back video signals.
Analog audio tracks contain sound signals. Control tracks contain signals that keep a tape playing back at the proper speed and the video heads aligned with the video tracks. Analog audio tracks and control tracks are recorded by separate, stationary heads. Audio tracks run along one edge of the tape, and control tracks along the other. Not all recorders use control tracks.
In professional digital videotape recorders, both the video and audio signals are recorded in helical scan tracks. In most digital recorders, both the video and audio signals can be recorded and edited separately. Digital recorders have error correction systems that ensure the playback of signals without visual or audible defects.
Playback.
As tape passes over the heads during playback, the tape’s magnetic patterns create a varying magnetic field in the head. When the magnetic field reaches the wire coil, it is converted into electric voltage. The varying voltage, which contains the audio and video signals, is sent to a television set, which transforms it into sounds and pictures.
History
The development of videotape recorders began during the 1940’s. However, the first videotape recorder that was capable of recording a television picture of broadcasting quality on magnetic tape was not invented until 1956. This reel-to-reel machine, produced by the Ampex Corporation of California, featured four heads mounted on a rotating wheel.
In 1959, the Toshiba Corporation of Japan introduced the first single-head helical recorder. This VTR, which was smaller and less expensive than previous recorders, helped videotape recording spread outside the television industry. By the mid-1980’s, two main types of home VCR systems, called Beta and VHS (Video Home System), had been developed. In 1985, Sony Corporation of Japan introduced the 8 mm VCR system. This system used 8-millimeter tapes in camcorders. In 1995, manufacturers introduced the first digital camcorder for home use. It used 6.35-millimeter tapes called DV’s or MiniDV’s.
Starting in the late 1990’s, manufacturers introduced other recording devices to compete with VCR’s. These devices include digital video recorders (DVR’s), also called personal video recorders (PVR’s). DVR’s can record and store 100 or more hours of television programs as a digital file, on a hard drive similar to that of a computer. Manufacturers also developed systems to record programs on special DVD’s. Today, some camcorders also record on hard drives or DVD’s. See DVD.
