A VCR isn't that mysterious of a device, but each one is a marvel of careful engineering, electronic precision, and mechanical functionality.
The VCR, or videocassette recorder, is a common piece of home entertainment electronics that plays back pre-recorded VHS videotapes. In addition, it has the capability to record video, even when unattended.
INS AND OUTS
One of the most striking things about the VCR is its versatility. Almost all VCRs can record live broadcast television signals, video from non-TV sources, or cable television. The VCR's flexible electronic tuner allows it to adjust to either broadcast TV or cable, and most can detect and store the frequencies where valid stations are broadcasting. Many can even scan for stations that broadcast a time-of-day signal and program the VCR's clock automatically.
VCRs also commonly include inputs to allow users to record external video from sources such as camcorders and videogame consoles. These inputs are generally in the "composite" or "RCA" form - usually a set of three female jacks that look like hollow, metal-rimmed cylinders, one colored yellow for video, and two (red and white) for audio. Higher-end VCRs can accept better-quality signals in the less common S-video or component formats.
MASTER OF THE TIME
The other significant electronic component of a VCR is its ability to schedule recording even when the owner isn't present. The owner can specify a specific time for a program to be recorded, or set up a recurring recording event so he or she never misses a favorite program. VCRs also generally include accurate hard-wired programming that allows them to accomodate daylight savings time, year's end, and leap years.
GEARS AND MOTORS
The VCR also has a significant physical component - the tape mechanism that does all the recording. The mechanism is very much like a cassette tape recorder: it moves the magnetic tape from the VHS cassette over a playback or recording head at a steady rate of speed, allowing the transfer of the video signal to or from the tape. (A recording head is a component that rearranges the iron particles in the tape into patterns that store the video signal at the point of contact with the tape. A playback head is a component that can read those patterns as a video signal.) When you put the tape into the VCR, the VCR actually flips a protective cover up at the front of the tape, unlocks the tape so it can move freely, and spools a length of tape out of the body of the cassette. That length of tape is precisely positioned over the playback and recording heads and gripped between rubber rollers, ready for action. When playback or recording begins, the tape moves forward, and of course, played tape is fed back into the cassette's take-up reel (the right side of the tape) as fresh tape is pulled out of the supply reel (the left side).
The playback and record heads actually use "helical scan" to transfer the video signal quickly to the tape. This means that the head is mounted at an angle to the tape, like a top tilted to one side. You may have seen this if you've ever opened a VCR or peeked into one from the tape bay. The head itself spins at high speed to transfer all the video and audio data to or from the tape. If the heads were fixed, like those of a cassette deck, the tape information would have to be much less dense, and the tape would have to travel at enormous speeds through the machine. At that rate, VHS tapes would be very large and heavy to contain all of the tape required to store two hours of programming!
You may have heard manufacturers mention "four-head VCRs." These VCRs have a playback and a record head for both the SP (two-hour) and EP (six-hour) tape speeds to create stronger, more defined video signals on a tape and more accurate, distortion-free playback. Some VCRs also have an "flying erase head" that wipes the signal from a tape during recording, just ahead of the recording head. This gives the recording head a nice, clean signal-free tape to record on, resulting in a better picture when the tape is played back, free of rainbow effects and noise.
THE LAST NON-DIGITAL VIDEO MACHINE
Unlike a DVD player or recorder, a VCR is non-digital. That means the video signal is never converted to a stream of digital, binary data - it's an analog signal that gets recorded as-is, right to the tape. It's very much like a vinyl record, not like a CD. It's prone to hiss, snow, tracking problems, and degradation. The most significant drawback is in picture quality and reproduction. Every time you make a copy of a VHS tape, the copy is lower quality than the original, and copies of a copy are even less impressive.
However, the VCR still can be a useful appliance in today's digital entertainment world. Unlike DVD recorders, they're inexpensive. Unlike Tivo units and digital video recorders (DVRs), they don't require monthly subscriptions to television programming services. Until DVD recorders and DVRs become commonplace, the VCR is the staple for capturing the programming we can't miss.
