Later helical scanning recorders instead usually use a method called "'slant azimuth recording "', also called Symmetric Phase Recording.
2.
Tapes recorded on a machine made before 1995 tend to not play well on newer machines due to slight changes in helical scanning head design.
3.
For detection, as opposed to tracking, the system also included a helical scanning mode that allowed it to search for aircraft . This mode had its own dedicated PPI display for easy interpretation.
4.
For recording this prevents overmodulation on analogue systems which tends to corrupt adjacent tracks in helical scanning; while on digital systems the peak signal amplitude is an absolute numerical value and cannot be exceeded.
5.
Helical scanning was a logical progression beyond an earlier system ( pioneered by Ampex ) known as field was broken into sixteen stripes on the tape ( which required appropriately complex head-switching logic ).
6.
Transverse scanning was superseded by the later technology of helical scanning, which could record one whole field of video per helically-recorded track, recorded at an angle across the width of the tape.
7.
While the quadruplex recording system per se is no longer in use, the principle evolved into the helical scanning technique used in virtually all video tape machines, such as those using the consumer formats known as VHS and the briefly successful Sony Betamax format . ( Sony Betacam was successful as a professional format, but operated with a different recording system and faster tape speed than Betamax .)
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