Editing VHS (section)

=== Cassette and tape design ===

[[File:VHS cassette tape 12.JPG|thumb|Top view of VHS with front casing removed]]
The VHS [[Videocassette|cassette]] is a 187&nbsp;[[Millimetre|mm]] wide, 103&nbsp;mm deep, and 25&nbsp;mm thick (7{{frac|3|8}} × 4{{frac|1|16}}× 1 inch) plastic shell held together with five [[Screw|Phillips-head screws]]. The flip-up cover, which allows players and recorders to access the tape, has a latch on the right side, with a push-in toggle to release it (bottom view image). The cassette has an anti-despooling mechanism, consisting of several plastic parts between the spools, near the front of the cassette (white and black in the top view). The spool latches are released by a push-in lever within a 6.35&nbsp;mm ({{frac|1|4}} inch) hole at the bottom of the cassette, 19&nbsp;mm ({{frac|3|4}} inch) in from the edge label.{{citation needed|date=November 2019}} The tapes are made, pre-recorded, and inserted into the cassettes in [[cleanroom]]s, to ensure quality and to keep [[dust]] from getting embedded in the tape and interfering with recording (both of which could cause signal dropouts)

There is a clear tape leader at both ends of the tape to provide an optical auto-stop for the VCR transport mechanism. In the VCR, a light source is inserted into the cassette through the circular hole in the center of the underside, and two [[photodiode]]s are on the left and right sides of where the tape exits the cassette. When the clear tape reaches one of these, enough light will pass through the tape to the photodiode to trigger the stop function; some VCRs automatically rewind the tape when the trailing end is detected. Early VCRs used an [[incandescent bulb]] as the light source: when the bulb failed, the VCR would act as if a tape were present when the machine was empty, or would detect the blown bulb and completely stop functioning. Later designs use an infrared [[Light-emitting diode|LED]], which has a much longer life.{{citation needed|date=November 2019}}

The recording medium is a Mylar<ref>Noble, Jem. "VHS: A Posthumanist Aesthetics of Recording and Distribution." OxfordHandbooks. Oxford Handbooks, Dec. 2013. Web. September 30, 2015.</ref> [[magnetic tape]], 12.7&nbsp;mm ({{frac|1|2}} inch) wide, coated with metal [[oxide]], and wound on two [[Bobbin|spool]]s.

The tape speed for "Standard Play" mode (see below) is 3.335&nbsp;[[Centimetre|cm]]/[[Second|s]] (1.313 ips) for [[NTSC]], 2.339&nbsp;cm/s (0.921 ips) for [[PAL]]—or just over 2.0 and 1.4 [[metre]]s (6&nbsp;ft 6.7 in and 4&nbsp;ft 7.2 in) per minute respectively. The tape length for a T-120 VHS cassette is 247.5 metres (812&nbsp;ft).<ref>{{cite web |last1=Wallace |first1=Dillon |title=How long is my tape? What is the format? |url=https://southtree.com/blogs/artifact/how-long-is-my-tape-what-is-the-format |website=Southtree |access-date=2 March 2020}}</ref>