The head drum of a Hi-Fi NTSC VHS VCR; three of the six heads face the reader. The helical path of the tape around the drum can clearly be seen.

The same head drum with the rotating portion elevated for clarity

The rotating portion of the head drum showing the rotary transformer and three of the six tape heads used in this particular VCR

Helical scan or striping is a method of recording higher bandwidth signals onto magnetic tape than would otherwise be impossible at the same tape speed with fixed heads. It is used in video cassette recorders, digital audio tape recorders, and numerous computer secondary storage and backup systems. Image File history File linksMetadata Download high-resolution version (1600x1200, 171 KB) The head drum of a six-head NTSC (Hi-Fi) VHS VCR. File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Helical scan Metadata This file contains... Image File history File linksMetadata Download high-resolution version (1600x1200, 171 KB) The head drum of a six-head NTSC (Hi-Fi) VHS VCR. File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Helical scan Metadata This file contains... The videocassette recorder (or VCR, more commonly known in the British Isles as the video recorder), is a type of video tape recorder that uses removable videotape cassettes containing magnetic tape to record audio and video from a television broadcast so it can be played back later. ... Image File history File linksMetadata Download high-resolution version (1600x1200, 173 KB) The head drum of a six-head NTSC Hi-Fi VHS VCR, with the rotating portion of the head drum elevated for clarity. ... Image File history File linksMetadata Download high-resolution version (1600x1200, 173 KB) The head drum of a six-head NTSC Hi-Fi VHS VCR, with the rotating portion of the head drum elevated for clarity. ... Image File history File linksMetadata Download high-resolution version (1600x1200, 166 KB) The rotating portion of a 6 channel rotary transformer used in a six-head (4 head Hi-Fi NTSC VHS) VCR, showing three of the six heads on the head drum. ... Image File history File linksMetadata Download high-resolution version (1600x1200, 166 KB) The rotating portion of a 6 channel rotary transformer used in a six-head (4 head Hi-Fi NTSC VHS) VCR, showing three of the six heads on the head drum. ... The fixed portion of a 6 channel rotary transformer used in a six-head VCR. Two additional shorted turns improve the isolation of the two outermost windings from each other and from the other, innermost windings. ... A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa. ... The videocassette recorder (or VCR, more commonly known in the British Isles as the video recorder), is a type of video tape recorder that uses removable videotape cassettes containing magnetic tape to record audio and video from a television broadcast so it can be played back later. ... Compact audio cassette Magnetic tape is a non-volatile storage medium consisting of a magnetic coating on a thin plastic strip. ... The video cassette recorder (or VCR, less popularly video tape recorder) is a type of video tape recorder that uses removable cassettes containing magnetic tape to record audio and video from a television broadcast so it can be played back later. ... A 90-minute DAT cartridge, size compared to a AAA (LR03) battery. ... In computer storage, secondary storage, or external memory, is computer memory that is not directly accessible to the central processing unit of a computer, requiring the use of computers input/output channels. ...

In a fixed head system, tape is drawn past the head at a linear speed. The head creates a fluctuating magnetic field in response to the signal to be recorded, and the magnetic particles on the tape are forced to line up with the field at the head. As the tape moves away, the magnetic particles carry an imprint of the signal in their magnetic orientation. If the tape moves too slowly, a high frequency signal will not be imprinted — the particles' polarity will simply oscillate in the vicinity of the head, to be left in a random position. Thus the bandwidth capacity of the recorded signal can be seen to be related to tape speed — the faster the speed, the higher the frequency that can be recorded. A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa. ... To meet Wikipedias quality standards, this article may require cleanup. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... This article or section does not cite its references or sources. ...

Video and digital audio need considerably more bandwidth than analog audio, so much so that tape would have to be drawn past the heads at very high speed in order to capture this signal. Clearly this is impractical, since tapes of immense length would be required. (However, see VERA for details of a partially-successful linear videotape system.) The generally adopted solution is to rotate the head against the tape at high speed, so that the relative velocity is high, but the tape itself moves at a slow speed. To accomplish this, the head must be tilted so that at each rotation of the head, a new area of tape is brought into play; each segment of the signal is recorded as a diagonal stripe across the tape. This is known as a helical scan because the tape wraps around the circular drum at an angle, traveling up like a helix. Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images which represent scenes in motion. ... A digital system is one that uses discrete numbers, especially binary numbers, or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (an analog system). ... Methods and media for sound recording are varied and have undergone significant changes between the first time sound was actually recorded for later playback until now. ... This article or section does not cite its references or sources. ... VERA (Vision Electronic Recording Apparatus) was an early videotape format developed by the BBC in the 1950s. ... A helix (pl: helices), from the Greek word έλικας/έλιξ, is a twisted shape like a spring, screw or a spiral staircase. ...

There were a number of practical problems to be overcome with this system. The high tape/head speed could lead to rapid wear of both the tape and the head, so both need to be polished extremely smooth, and the head made of a hard wearing material. In addition, most systems operate with an air bearing separating the heads from the surface of the tape. Supplying signals to a rotating head is also problematic — this is usually accomplished by coupling the signal(s) inductively through a rotary transformer as shown in the third photograph. The transport mechanism is also much more complex than a fixed head system, since, during loading, the tape must be pulled around a rotating drum containing the head(s) so that a complete stripe can be recorded on each revolution. In a VCR for example, the tape must be pulled right out of the cassette case and threaded around the drum, and between the capstan and pinch roller. This leads to complex and potentially unreliable mechanics. Fluid bearings are bearings which solely support the bearings loads on a thin layer of liquid or gas. ... An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... The fixed portion of a 6 channel rotary transformer used in a six-head VCR. Two additional shorted turns improve the isolation of the two outermost windings from each other and from the other, innermost windings. ... The video cassette recorder (or VCR, less popularly video tape recorder) is a type of video tape recorder that uses removable cassettes containing magnetic tape to record audio and video from a television broadcast so it can be played back later. ... Capstans are found in the mechanisms of tape recorders in which they have a similar function to nautical capstans. ...

Azimuth recording

Every videotape system attempts to pack as much video as possible onto a given-sized tape, but information from one recording stripe (pass of the video head) can't be allowed to contaminate information on the adjacent stripes. One method to provide isolation between the stripes is the use of guard bands (unrecorded areas between the stripes), but this wastes valuable tape space.

Helical scanning recorders instead usually use a method called azimuth recording. The head drum usually contains two heads with the magnetic gap of one head tilted slightly leftwards and the magnetic gap of the other head tilted slightly rightwards. (The tilt of a magnetic head is referred to as its azimuth adjustment.) Because of the alternating tilts, each head will not strongly read the signal recorded by the other head and the stripes can be recorded immediately next to each other, alternating between left tilt on one television field and right tilt on the next television field. (In practice, it's not uncommon for the recorded stripes to overlap somewhat.) Azimuth is the horizontal component of a direction (compass direction), measured around the horizon toward the East, i. ...

Using azimuth recording, the need for guard bands is completely eliminated.

Contrast with quadruplex recording

Helical scanning was a logical progression beyond an earlier system (pioneered by Ampex) known as quadruplex recording. In this scheme, the rotating head drum ran essentially perpendicular to a 2 inch wide tape and the slices recorded across the tape were nearly perpendicular to the tape's motion. U.S. quadruplex systems revolved the head drum at 14,400 revolutions per minute (240 revolutions per second) with four heads on the drum so that each television field was broken into sixteen stripes on the tape (which required appropriately complex head-switching logic!). By comparison, the longer stripe recorded by a helical scan recorder usually contains an entire TV field and the two-headed head drum spins at the frame rate (half the field rate) of the TV system in use. Ampex is based in Redwood City, California. ... 2 Quadruplex (also called 2 Quad, or just quad, for short) was the first practical and commercially successful videotape format. ... Mid-19th century tool for converting between different standards of the inch An inch is an Imperial and U.S. customary unit of length. ... United States is the current Good Article Collaboration of the week! Please help to improve this article to the highest of standards. ... In video, a field is one of the many still images which comprise a They are similar to frames, but they have half the vertical resolution and are displayed twice as fast. ...