VHS - Signal Standards

Signal Standards

VHS can record and play back all varieties of analog television signals in existence at the time VHS was devised. However, a machine must be designed to record a given standard. Typically, a VHS machine can only handle signals of the country it was sold in. Because some parameters of analog broadcast TV are not applicable to VHS recordings, the number of VHS tape recording format variations is smaller than the number of broadcast TV signal variations—for example, analog TVs and VHS machines (except multistandard devices) are not exchangeable between the UK and Germany, but VHS tapes are. The following tape recording formats exist in conventional VHS (listed in the form of standard/lines/frames):

• SECAM/625/25 (SECAM, French variety)
• MESECAM/625/25 (most other SECAM countries, notably the former Soviet Union and Middle East)
• NTSC/525/30 (Most parts of Americas, Japan, South Korea)
• PAL/525/30 (i.e., PAL-M, Brazil)
• PAL/625/25 (most of Western Europe, Australia, New Zealand, many parts of Asia such as China and India, some parts of South America such as Argentina, Uruguay and the Falklands, and Africa)

Note that PAL/625/25 VCRs allow playback of SECAM (and MESECAM) tapes with a monochrome picture, and vice-versa, as the line standard is the same. Since the 1990s, dual and multi-standard VHS machines have become more common. These can handle a variety of VHS-supported video standards. For example, regular VHS machines sold in Australia and Europe nowadays can typically handle PAL, MESECAM for record and playback, plus NTSC for playback only (provided the TV is capable of displaying NTSC's 525-line/30 fps standard). Dedicated multi-standard machines can usually handle all standards listed, of which some high end models can even convert the content of a tape from one standard to another on-the-fly during playback by using a built-in standards converter.

S-VHS only exists in PAL/625/25 and NTSC/525/30. S-VHS machines sold in SECAM markets record internally in PAL, and convert to/from SECAM during record/playback, respectively. Likewise, S-VHS machines for the Brazilian market record in NTSC and convert to/from PAL-M.

A small number of VHS decks are able to decode closed captions on prerecorded video cassettes. A smaller number still are able, additionally, to record subtitles transmitted with world standard teletext signals (on pre-digital services), simultaneously with the associated program. S-VHS has a sufficient resolution to record teletext signals relatively error-free without any special measures taken (to see them during playback, the TV simply has to be switched into its normal teletext mode), but VHS does not.