Top view VHS cassette with US Quarter for scale

Bottom view of VHS cassette with magnetic tape exposed

The Video Home System, better known by its acronym VHS, is a recording and playing standard for video cassette recorders (VCRs), developed by JVC (ironically, with some of its critical technology under lucrative licensing agreements with Sony) and launched in 1976. VHS officially stands for Video Home System, but it initially stood for Vertical Helical Scan, after the relative head/tape scan technique. Some early reports claim the name originally stood for Victor Helical Scan system.

VHS became a standard format for consumer recording and viewing in the 1980s after competing in a fierce format war with Sony's Betamax and, to a lesser extent, Philips' Video 2000. VHS initially offered a longer playing time than the Betamax system, and it also had the advantage of a far less complex tape transport mechanism. A VHS machine can rewind and fast forward the tape considerably faster than a Betamax VCR since it unthreads the tape from the playback heads before commencing any high-speed winding. On the other hand, Betamax offers superior picture quality. See VCR for more details.

A VHS cassette contains a 12.65 mm (approx ½-inch) wide magnetic tape wound between two spools, allowing it to be slowly passed over the various playback and recording heads of the video cassette recorder. VHS tapes have approximately 3 MHz of bandwidth, and a horizontal resolution of about 240 lines per scanline [1] (http://www.hometheaterhifi.com/volume_6_3/essay-video-resolution-july-99.html). The vertical resolution of VHS is determined by the TV standard — a maximum of 486 lines are visible in NTSC and a maximum of 576 lines in PAL.

Several improved versions of VHS exist, most notably S-VHS, an improved analog standard, and D-VHS, which records digital video onto a VHS form factor tape. Devices have also been invented which directly connect a personal computer to VHS tape recorders for use as a data backup device.

Another variant is VHS-C (C for compact), used in some camcorders. Since VHS-C tapes are based on the same magnetic tape as full size tapes, they can be played back in standard VHS players using an adapter. The magnetic tape on VHS-C cassettes is wound on one main spool and used a sort of a gear wheel which moves the tape forward. It can also be moved by hand and so is the spool. This development hampered the sales of the Betamax system somewhat, because the Betamax cassette geometry prevented a similar development.

Top view of VHS-C, compact cassette

Bottom view of VHS-C, compact cassette

External links

• The 'Total Rewind' VCR museum, covering the history of VHS and other vintage formats (http://www.totalrewind.org)
• BBC News article: Death of video recorder in sight (http://news.bbc.co.uk/1/hi/business/4031223.stm)