In this section we are going to take a brief look at the machine methods used to capture and recover a video recording using magnetic tape (PLATE 1). We will explore the various steps that eventually developed into modern day video cassette recording. We already touched on this a little in the previous section but now we delve into the nuts and bolts.
Archiving past events is spawned by a special trait of we humans. We seem to be unique from all other living things. We are the only species (so far as we know) that desires to keep a record our memories, or more accurately, evidence of our past. It all started very early on as pictographs on cave walls and evolved into Gone With The WInd. It went from bragging about the big hunt, to keeping track of shipments, to doing it just for the fun of it. No other living thing on this planet purposely keeps a record of what has already occurred. Maybe we're the only one that wants too. Here now is a short history of how designers developed video recording, and ultimately ended up putting that awesome power into your hands.
One of the earliest ways to record sound was by rotating a wax cylinder and using a needle to make a grove in it. At this point mankind now knew that it could be done. Fast forward a little in time to the first reel-to-reel recorders like the one shown on the left in the photo (PLATE 1). This is a wire audio recorder. One of the first devices that could record sound as well as play it back, and do it over and over. Instead of using spool of magnetic tape a wire made out of a special material was magnetized and then rewound and played back. AS shown a wire can be magnetized just like a thin film covered with metallic particles. It seems primitive but at the time this was the best there was. (Magnetic tape hadn't been invented yet by 3M.) The principles involved in wire recording have a lot in common with video recording. In the wire recording process a spool of wire rich in iron is passed across a recording head (an electromagnet ) energized by an incoming signal from a microphone or some other source. This causes the microscopic iron particles in the wire to acquire a variable magnetic charge that is unique to the signal being introduced. Once the recording has been made the wire can then be rewound and passed back over the head that now acts as a pickup, this reverses the process for playback. During recording the head is active and for playback it is passive. The recording can be played back again and again and also be recorded over and over. (I know we covered this in some detail in the previous section called "THE BASICS" but it is worth refreshing.) It is the conversion process is what makes it all work. Not to sound corny but just shouting at the wire would accomplish nothing. This conversion process is used time and time again in the world of electronics. One the right in the above photo is a recorder similar to the wire unit but it uses audio tape. Here the iron particles have been ground up to a micro fine powder and then glued to a thin plastic strip. Tape came after wire because the technology had to wait for the development of acetate film, and then later, polyester. So wire disappeared and tape took its place. Recording video never had a wire recording stage but it did go through some growing pains. Now let's take a look at some devices used to make an archive of a television signal. Click on the photo (PLATE 2).
What you see here are several devices that used photographic film to make a record of a television show. The large item on the left is a Kinescope or telecine machine. The device in the upper right is similar. They were used in the days before television was recorded on video tape. It was a relatively simple process. As you can see from the photos a motion picture camera was pointed at a small TV screen and what appeared on the tube was photographed as a movie. The results were grainy, flickered a lot and were in black and white (no color back in the old days). The TV picture was simply being converted to film, and much of this survives to this day. Magnetic recording of TV would have to wait for a dependable thin recording tape to be developed. In the lower right in the above photo is a machine that turned the process of kinescope around. Here a projector sent an image from a motion picture film into a television camera, which allowed it to broadcast over television (or placed later on to tape, DVD or any other of a dozen chosen media). This is the just reverse of the other devices and it is still being used today.
Click on the photo again (PLATE 3) and here we the first broadcast video tape recorder. Certainly not suitable for the home it was called the Quadruplex system. As you can see it used very large reels because the tape was wide and traveled rather quickly through the machine. (Because lot's of information is required to record and play back a television picture.) Look in the upper left corner and a diagram shows that the unit had spinning heads (called the scanner) that turned at a ninety degree angle across a two inch wide magnetic tape. Because the quality of the recording tape during these early times wasn't as good as it is today it had to be wide and it had to travel through the machine at a fairly high speed. Because the scanner was a round cylinder the tape had to be curled. This made it difficult to splice if you wanted to do any editing. But it was good enough for network broadcasts, and the recordings could be in color. There are several other drawbacks to this system. For remote recording you had to have a special truck to accommodate the massive amount of equipment needed. To ship tapes back and forth require big cans, similar to movie theater film cans. The tape was also sensitive to weather conditions because it was so large and thin. Quadruplex was used for quite a few years until the introduction of a new, much handier process came along, and we are going to look at it next. Click on the photo once more (PLATE 4). Technology improved but more importantly magnetic tape got a lot better. The micro fine iron grinding process was developed so the particles could be made a lot smaller. Tape could now accept a lot stronger signal in a much smaller space. Equipment manufacturers developed machines to take advantage of this. The rewards for these improvements were huge. There were a lot of television stations, businesses, institutions, etc. that wanted to take advantage of an easier way for recording video. Even more impressive was the vast audience of television viewers that was growing at very rapid rate. Television station that could provide the best recordings and the fastest service were in a better position to ask for that higher advertising dollar (think news gathering). Sony was one company that developed an improved, small reel-to-reel video recorder that employed a "helical" scanning drum. Helical simply means that the tape traveled around a video drum and the video heads rotated across the tape at a long angle (not in a 90 degree angle as with Quadruplex). Several samples of a portable reel-to-reel video recorder are seen at the top in the photo. The scanner (or video drum) can be seen lower left and the audio, control and capstan components are shown lower right. The extended recording area (or scan) allowed for a less wider tape to be used that could hold a lot of information traveling at a slower tape speed. This was ideal for mobile television. Sony also was ahead of the competition by having snapped early on to the value of the transistor just developed by bell labs (Western Electric). With it they could make their units smaller, more portable and they could be very cost effective. No tubes were needed. Remember when TVs in them had hot tubes filled with gas in them that went bad over time?
Next we look at just how Sony, along with others, changed video recording forever as we continue our discussion with the U-matic and the early days of cassette recording. To go to the next subject about the first cassette cartridge recorder click here.
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