Cassettes
A VHS cassette works according to the same principles as an audio cassette. It contains a spool of magnetic tape upon which the film has been encoded. The spool is threaded between two reels on the inside of the tape, protected by a plastic outer shell. The tape runs from one spool across the front of the VHS tape and onto the other spool, guided by rollers to keep it on track. A flexible plastic door covers the spools when the cassette isn't in a VCR to keep the tape from being damaged. In addition to the film, the tape also contains data on the play speed: SP, LP or EP, depending on the speed the original recording was made.
VCR
A VCR is designed to read the data on a VHS tape and translate it for playback on a television. A drum inside the VCR contains two recording heads, which perform this duty. When a tape is placed in a VCR, the plastic door is lifted and a set of rollers extends the tape around the drum. The drum then turns, reading the data on the tape and advancing it through the mechanism back onto the cassette. The data is then translated into scan lines and broadcast on your television as a moving image. A clear piece of material sits at the end of the tape, which a VCR detects by shining a light through it. It can then stop the tape and begin the rewinding process.
Recording
A VCR recording is created in a manner similar to playback. A tuner in the mechanism picks up the broadcast from a given station. It then turns the signal into data and transfers that to the tape as it passes over the recording head. Once the data is on the tape, it can be rewound and played back as normal. It often helps to erase the previous data on a VHS tape before recording on it (it provides a better picture). Flying erase head VCRs have a mechanism that facilitates this while a recording a tape.
Obsolescence
VCRs facilitated a revolution in the way people watch and enjoy entertainment. Newer technologies have eliminated many of the problems VHS cassettes faced. DVDs and Blu-ray discs are not as fragile as VHS tapes, and because they record digitally, their image quality is much higher. Even more importantly, the discs have no moving parts and nothing is required to contact their material in order to retrieve the data they contain. That means they won't wear out the way VHS tapes do, providing a much longer shelf life and pristine image quality to boot.
Tags: data tape, image quality, plastic door, then turns
