SWS Security
White Papers
"In God We Trust. All Others We Monitor."

 

video surveillance

This article was published in Police & Security News Magazine

Care and feeding of video systems, plus some theory and practical comments on video stuff

This article will discuss how to get the most out of your investment in video technology. We'll cover a bit of the basics of video, how to select the best equipment, hints on operating it, how to maintain it, how to process and store videotapes so they work when you need them. We'll also discuss what can and can not be done with video.  

Video is an extension of our eyes. Much technology, particularly surveillance, is the practice of using electronics to extend the range of our senses. 

Video evidence is a critical part of investigations. Much surveillance is conducted with the hopes of obtaining desired video. Hundreds of thousands of dollars are spent on surveillance operations where the primary, and sometimes, only, real fruits are on videotape. Surveillance types install hidden cameras and timelapse video recorders in areas where nasty things occur. Bank cameras and other security cameras record everyday activity and store that activity on tape or disk for review later if needed. Depositions are recorded on videotape. Split second sports finishes are recorded on video. 

Your wedding, or your child's birth may have been captured on video, preserved for all time. 

Read on so you can get the most out of your investment in video. 

 Spending the Hours Reminiscing 

Not all that many years ago, video cameras had vacuum tubes in them. CCTV (Closed Circuit TV, as opposed to broadcast) cameras were large (typically the size of a shoebox), heavy, drew a lot of power, got hot, had limited lifetimes, were expensive, had operating quirks all their own. You couldn't point them at the sun or the image tube would burn in short order. You couldn't point them down, because loose particles in the tubes would scrape phosphor off the inside of the image tube face and degrade the picture. You couldn't leave them looking at the same scene for long periods, or that scene would burn itself into the tube and you'd still see the image even when you pointed the camera somewhere else. You couldn't run them on 12 volts DC without a lot of hassle. Some cameras needed power supplies as large as the camera itself. The cameras needed mechanical and electrical adjustment, especially as they aged. A 2 year old camera would need the beam current adjusted several times a year, and doing this properly required some test equipment and experience. 

Rude and crude as they might have seemed, zillions of these cameras were in service. Thousands of bad guys were put away with evidence collected by those old boat anchors. 

Tube cameras, then and now, offered a high level of performance and a fair degree of reliability.  

Now, tube cameras are all but obsolete except for certain very high performance applications like some broadcast, medical imaging, very low light and a few others. The very best modern chip cameras have no better resolution than did the average tube camera ten years ago.  

Not all tube cameras were large. Remember the Sony Watchcam? That was the first miniature consumer video camera small enough to be practical for everyday surveillance. The Watchcam was cigarette-pack sized, ran on low voltage DC, had a built in auto iris lens and an internal microphone. It delivered a surprisingly good image even in low light. The cables and connectors were pre wired, so no tools or skills were needed to install them. Plug and play.  

The Sony Watchcam used a tube image sensor (the "Saticon"). Filaments and all. When this camera came out it was inexpensive and widely advertised in the security circles, resulting in thousands of burglar alarm company billing themselves as "surveillance" companies. I know of several Watchcams still in use today, more than fifteen years later, and still doing the job. Sony did a marvelous job with the Watchcam series, opening the door to reliable, effective and inexpensive covert video pretty much for the first time. Prior to the Watchcam, professional covert video was restricted to experts due to the limited availability of equipment, therefore genuine skill was needed to substitute for the lack of small cameras and lenses. 

Stay tuned. We're about to learn what makes a video system, and what the various components of a video system do. 

Let's quickly cover the basics so we all are talking the same language. 

What makes a video system? 

A video monitoring system, such as might be installed in a retail store to watch for shoplifters, consists of several components. Each is important. Each has special selection criteria and maintenance requirements. 

There is, of course, the camera. There's a power supply for the camera. Usually a mounting bracket. A lens is needed. The lens could be an integral part of the camera or a separate item. The camera sounds sexiest and thus gets the lion's share of attention. 

What is the basic purpose of a video camera? One definition is to remote our eyeball to somewhere it can't be, or to provide a signal to be recorded in some media other than our brain.  

The camera's reason for being is to convert an image in real life into some sort of signal we can do something with. We might want to record the image, monitor it, conduct it or radiate it somewhere else where it can be recorded or monitored. Depending on the type of camera and the application, and to an extent your budget, you may convert the image the camera sees into an electrical signal, an optical signal, an audible signal, or even a chemical signal (biological data memories are real). Some of these signals might be analog, some might be digital. The real world starts and ends analog, for your information, and most interfaces with the human senses need to be analog, or converted to analog if they were digital.  

Once the video signal comes out of the camera in our mythical retail emporium, we have to get it to somewhere where we can watch it and record it. We generally can assume we need to transmit the signal somewhere, or we wouldn't need the video system (we could just look with our eyes and not need the electronics).  

There are two common methods to get the video signal from the camera to wherever we need it. These methods are conducted, and radiated. 

Conducted, as you might expect, is sending the video signal along some sort of metallic or optical conductor, where a physical component other than atmosphere carries the signal. Popular conductors are the time-tested coaxial cable, and, more recently, twisted pair aka telephone-type wiring or computer network cabling, also via fiber optics. Video also can be sent, anywhere in the world, via the dial up telephone network, but this is a special purpose application and not pure video as we come to expect. We will not get into that here. 

The classic method of conducting video from one place to another is via coaxial cable aka coax. Coax for video typically is about the diameter of a pencil. It consists of a stranded or solid center wire conductor covered with plastic insulation. Over that insulation is a braid of fine wire, serving as a shield. The center conductor is one side of the video, and the shield is the other. Special connectors must be used, with one called a BNC being the most common.  

Coax is cheap, proven, relatively low loss over short runs, relatively easy to work with, and has a fair longevity of several years. Properly selected and installed, coax is a good choice. 

An alternative becoming more and more popular is video transmitted along twisted pair cable. Twisted pair is ordinary small gauge telephone wire. Also in common use is Category 5 (CAT 5) computer network cable. In many instances, existing cabling can be used, allowing you to hang a surveillance somewhere without having to run a lot of cable. If you use Cat 5, extra pairs can be used to provide power for the camera. 

Video by itself does not transmit well over twisted pair. Therefore you use twisted pair video modems, which convert the video to levels and impedances which can transmit efficiently over twisted pair wiring. Twisted pair modems for short runs (maybe 1500 feet maximum) are half the size of a pack of cigarettes and require no power. Generally they have a BNC connector for video and two screw terminals to connect the twisted pair. The modems are symmetrical, meaning the same unit can be used for both the send and receive end. 

The twisted pair modems cost a bit, but the expense may be recovered many times over if you can avoid the cost and labor to install coax. The longer the run the more economical twisted pair modems will be. 

For long runs (over several thousand feet), powered modems are used. These are the same as passive (unpowered) ones except you connect a small wall transformer to power an amplifier. It is possible to mix powered and unpowered modems. 

Advantages of twisted pair modems are the ability to drive long runs of inexpensive cable, and the potential to use existing cabling instead of having to run something special, and ease of use. The primary disadvantage is cost. In my opinion, the cost is negligible for the benefits offered. I can see the end of coax for video transmission in the near future. 

Several manufacturers offer twisted pair modems. I am sure all work fairly well. I have been pleased with the cost and performance of modems from Northern Video Technologies aka NVT. The original concept appeared in a small article in Electronic Design magazine some years ago, and all the existing products sprang from that original work. 

Video also can be transmitted over conventional dial up telephone lines. A video image can be transmitted theoretically anywhere in the world over conventional or cellular telephone. While it does work, there are many tradeoffs. 

The bandwidth, or capacity to carry information, of a telephone line is rather limited. The phone system was designed to transmit speech. Not much information needs to be transmitted for voice. 

Standard video is a very wide bandwidth, far wider than the ability of the phone line to transmit it. Also, phone lines transmit sound, not pictures. What do we do? 

Full motion video consists of 30 frames a second. This is like 30 still pictures flashing by every second. To our eye, this looks like full motion. 

For phone line video, we take one frame, store it digitally, and transmit it slowly over the phone line. The slow transmission is within the limited capability of the phone system. At the other end, the information is stored, reassembled into a frame and displayed on a monitor. 

The equipment used in phone line video also takes the video frame and converts it into tones. These audio tones are transmitted over the phone line. Remember the phone line can handle audio only. 

The time it takes to transmit a frame of video depends on the resolution you desire. A rough image can be transmitted in maybe 15 seconds. A fairly decent one takes 30. A high resolution detailed image can take one or two minutes. Watching phone line video is like watching a slide show. The type of transmission is called "slow scan", meaning the scan rate of video is slowed w-a-y down from 30 frames a second to perhaps one frame every 30 seconds. 

More about the composition of video, frame rate, etc. is covered below under Time Lapse Recorders.   

There are some advantages to phone line video. A classic example is auto sales lot monitoring. One guard in one location can monitor video from numerous car lots over the telephone. Each lot has equipment which will initiate a phone call and video transmission to the listening post when movement is detected in the area. This setup allows one guard to watch multiple locations, and obviously a tremendous savings in manpower. Phone line video also can be used to verify alarms so the appropriate level of response can be assigned. You can imagine all sorts of surveillance applications.  

Disadvantages are the cost of the equipment which is not insignificant, general lack of experience in applying phone line video, and the slow transmission speed.  

Phone line video is a special solution for special problems. It has its place but must be carefully and intelligently applied. 

Radiated video means, generally, without wires. This would encompass primarily wireless video transmitters (where the signal is sent via RF, or radio wave), and to a lesser extent infrared and laser links where the video signal modulates a light beam. Ordinary broadcast television is wireless video, although we don't usually think of it in those terms. I have written several articles discussing wireless video at great length, so I merely will refer anyone interested to those articles and not repeat the information here. 

Now we have our video signal at the other end of this conducted or radiated path. We can watch it using a video monitor, or record it using a video recorder. 

A video monitor does the opposite job of the camera. It converts the electrical (video) signal into something our eyeballs can see. A video monitor outputs, hopefully, an accurate reproduction of what the camera was seeing. Monitors look like televisions, and in fact a television contains a video monitor plus some other circuitry. Monitors can be black and white, or color. Most, even today, still use a tube (Cathode Ray Tube aka CRT, or picture tube to the television industry), although solid state monitors are becoming more common. Right now, but not for long, highest performance and lowest cost are with tube-based monitors. Tube monitors can have lifetimes measured in thousands of hours. They are larger than solid state, heavier, draw more power, are less rugged generally, have higher specifications and better performance. CRT monitor technology is well developed although solid state is taking over and will be the standard within a few years. Most smaller CRTs, such as are used in oscilloscopes, no longer are in production and manufacturers are being forced to redesign around solid state replacements. Liquid Crystal Displays (LCDs) are the most common solid state display, although there are many others. Your laptop computer screen is a good example of an LCD display. 

Not too much to say about video monitors. You get what you pay for. Remember though, all the other fancy video goodies depend on the monitor for their performance. Doesn't matter how beautiful the color, how low light or anything else wonderful the camera can do, if you can't reproduce that on the monitor. Fortunately, excellent monitors are inexpensive and reliable, and the performance of even inexpensive monitors generally exceeds that of expensive cameras. 

Next is the video recorder, commonly called the VCR, for Video Cassette Recorder. An earlier term was VTR for Video Tape Recorder, when open reels of tape were used, and before cassettes were the standard. This term may not be accurate too much longer as tape recording for many applications is being replaced by digital storage generally to disk. The video recorder has a very important job in the overall scheme of video. Its job is to record what the camera sees, for later use. This is where trouble starts. Much more later in this article.  

Camcorders 

A camcorder is a primary tool for many investigators in both the public and private sector. Camcorders are relatively recent inventions, and consist of a video CAMera and a video reCORDER in one package. Many of us remember the days before camcorders, when "portable" video meant a large video camera with a large lens sitting on your shoulder, and a larger video recorder hanging on a shoulder strap. Now, excellent high performance camcorders are inexpensive, reliable and compact. We're spoiled. 

Virtually all of the following discussion on fixed cameras and recorders also will apply to camcorders. For all practical purposes they are the same, except for packaging. 

So far in this article, we've learned about the various parts of a video system and discussed them in detail. Now we will pick up on video tape, a critical but often ignored part of the video system. 

Care and Feeding of Video Tape: What is video tape, anyway? 

We take the proper operation of our video equipment for granted. We ASS-U-ME our tapes will play back properly when needed, a week or a year later. 

For many of us, ignorance is bliss. This stuff continues to work in spite of our best efforts to ignore the proper selection of equipment, maintenance, proper handling of the magnetic media. We're lucky.  

A video recorder is a central component of a video system. Moving in more closely, video tape is the critical component of a video recorder. Tapes are not to be chosen and handled casually. From purchase to initial use to storage, proper care will provide much more reliable video, higher quality images and the most for your investment. 

Images recorded on videotape are recorded magnetically. Remember this and some of the following information might make more sense. 

Video (and audio) tape consists of a plastic backing (the tape itself, called the substrate), and a magnetic coating. The magnetic coating basically is iron oxide, or rust, finely powdered, mixed with a binder, and spread as a coating on the substrate. You can think of magnetic tape as a strip of plastic coated with rust. Better quality tapes may have a lubricant applied also, to reduce wear as the tape moves across the video heads. 

Video heads?  

In a typical video recorder, the video signal from the camera, and audio if you are using it, are fairly weak signals. They are amplified, some black magic (pre-emphasis, biasing) is performed to compensate for the physics of magnetic recording, then the signals are sent to the recording "head". The head is a coil of fine wire wound around a ferrous core in a horseshoe shape, with a very narrow gap between the ends. Ferrous means a material capable of being magnetized, but is not itself necessarily a magnet. Ferrous materials almost all are some form of iron. You know you can make a magnet out of iron, but not aluminum. That is because iron is ferrous, and aluminum isn't. Ferrous is a Latin derivative of the word "iron". 

The continuously varying video signal voltage pushes a likewise varying amount of current through the recording head. The coil with current flowing through it makes an electromagnet, which you will remember from high school physics. The varying current makes a varying magnetic field. 

The magnetic tape is moving across the gap in the recording head at a certain relatively precise speed. As it moves across, the tape is magnetized in proportion to the video signal pushing current through the recording head. 

There's your recording. 

Your video tape has magnetic fields stored on it in proportion to the video signal. 

Playback is the opposite of recording. 

The previously magnetized tape is pulled across a similar playback head, at the same precise speed. Although the heads are very similar, and in fact in inexpensive audio recorders the same head is used for both record and playback, there are some minor differences in the engineering which, in quality recorders, dictate separate record and playback heads for best performance. 

As the magnetized tape is pulled across the playback head, the magnetic field from the tape moving across the head works in reverse, generating a weak electrical signal out of the head in the precise manner the alternator works in your car. This signal is amplified, some black box processing is applied, and the louder signal drives the video monitor. The video monitor takes the video signal and changes it into a picture our flesh and blood eyeballs can interpret. 

Simple, now that we've learned how it all works. It really is simple, and if the process is not clear in your mind, please reread the above material. An understanding of the process of magnetic recording and playback will serve you well in the future, maintaining and using magnetic recording equipment. 

An interesting snippet of history   the earliest magnetic (audio) recording actually used very fine iron wire as the magnetic media. They were called wire recorders, oddly enough. I believe wire recorders existed into the 1950s when plastics technology became affordable and tape was developed and refined. WW2 recorders were wire recorders, and provided surprisingly good fidelity for speech and some music. The wire was very fine gauge (hair sized) and thus fragile. Also, it rusted so it needed to be stored in low humidity. The spools of wire were fairly heavy, and about the diameter of a large coffee mug with a large hole in the center. Later, the iron wire was replaced with stainless steel to prevent the rusting problem.  

The small diameter of the wire limited the amount of information a given length could hold, therefore for acceptable fidelity the wire was moved past the heads at high speed. The less information a tape can hold, the more of it and the faster it needs to be transported past the heads, and the less time you can record on a given length of tape. Video is a lot more information than audio, so video tapes tend to be wider than audio tapes, and move faster past the heads than audio tapes. The earliest video tapes were very wide, about the width of a playing card in the smaller dimension. The tapes moved very very fast, meaning it took very large (and heavy) reels of tape to last any practical length of time. A typical early reel might hold nearly 2 miles of tape (10,000 feet), and the reels were so heavy and moved so quickly that large motors were needed. The operators also needed to wear leather gloves for safety, for instances where the tape snapped and they had to slow a runaway reel by hand while it spilled tape all over the floor, or when the tape ran out and the full takeup reel was screaming away with all that inertia. 

Technology is interesting. 

OK, it's all very interesting, but why do we care? 

Good question. 

First of all, remember that all recording tapes are magnetic media. Keep magnets away from them. Far away! 

Tapes can be erased, partially, by even weak magnetic fields. Weak fields can cause lots of damage if over a long period of time. Strong fields can wreak havoc in a much shorter period. The first things to go are the high frequencies which provide the "sharpness" in the image. Next is color. Last is the basic black and white picture.  

Tapes must be kept away from anything magnetic, or anything electrical which can create a magnetic field. Motors, tools, refrigerator magnets, magnetic paper clip dispensers, transformers of all sorts (wall warts), even the magnet in speakers in audio devices all can degrade magnetic tape. Computer monitors as well as video monitors, especially those in plastic cases, emit magnetic fields strong enough to be a problem. Do not store videotapes on top of monitors! Computers also emit magnetic fields, and there is a motor for the fan in most computer power supplies. 

Just because you've committed some of these sins for years and gotten away with it does not mean your luck will hold forever. 

New tapes are the best to use for important work  right? 

Well, contrary to what you might think, actually, NO! 

New tapes are wound at high speed into the cassettes. This high speed causes a packing,  or slight sticking, which may not let the tape feed freely at normal operating speeds. That means the tape may not be at the precise mandated speed and may cause problems in synchronization of the video, or cause wow and flutter in the audio. Wow is a term for slow speed variations, and flutter is the term for high speed. 

Also, new tapes tend to have an oil presence from the initial outgassing of the plastic case. You frequently can smell this when you unwrap a brand new tape. Lubricated tapes may have lubricant buildup on the surface, not absorbed into the coating yet. This oil or lubricant can crud up the video heads, killing performance for all tapes, not just this one. 

New tapes also tend to have manufacturing dust on them. This dust is loose oxide from the tape, dust from the paper label or cardboard sleeve, or from other manufacturing processes. 

The best thing to do with any new tape is to fast forward and rewind it before using it for the first time. This is very important, one of the best things you can do to insure good recordings. It's also free. Do this for any type of magnetic tape: video, audio or data. The official term for this process is "retensioning" the tape. If you remember nothing else from this article, remember to retension the tape. 

Also, before using, retension any tapes that have been in storage for more than a month or so. This is equally important, for best tape life as well as for best quality record and playback. 

I cannot stress enough how important the winding cycle is to proper performance of magnetic tapes. When I was with a government agency early in my career, technical types were sent to a nearby NASA school to learn tape recorder theory. NASA has special machines, called winder/cleaners, specifically to process new tapes before they are used to record critical data sent down from spacecrafts. NASA facilities also have entire sections with nothing but winder/cleaners and a full time staff hanging tapes from the library on the machines. All the archived tapes are rewound every month or so, to insure the data is good when they need it. Millions of your tax dollars were spent learning this. 

You don't need an expensive winding machine. For low volume you can just use your camcorder. For higher volume, invest maybe twenty bucks in a tape rewinder which also has a fast forward function. You also can use a trashed VCR as a rewinder, as long as the mechanical tape transport is functioning. 

Best is if the winding/rewinding is done in one operation, not interrupted part way through. 

And the tapes will last the longest if rewound before storage. You want to minimize exposure of the tape and the oxide surface to atmosphere. Remember, the oxide basically is rust, and the rusting process can continue under the proper conditions. 

Do not touch the tape with your fingers. Your fingerprints contain skin acids as well as skin oils. God only knows where your hands have been. 

To answer the original question: No, new tapes are not the best bet. Preferable are good quality tapes which have a few passes on them and which have been stored properly.  

Stored properly? 

Yeah. Videotapes are precision devices. They are a marvel of engineering in that a quality tape can be manufactured for much less than a dollar, in enormous quantities, for consumer use in all sorts of grungy machines, and still give reliable service.  

The optimum storage conditions for magnetic tape has been determined by government and industry. The best storage conditions are a temperature of 68 degrees F, with a relative humidity of 40 percent. The environment should be as dust free as possible, and packaging material should not contain any acid-based chemicals. Acid based chemicals are found in glues and corrugated cardboard boxes as well as adhesive labels. Don't smoke around tape storage, as the tape movement builds up a static charge on the tape, and this charge is a magnet to smoke particles. 

Here's another important tip   Store videotapes in sleeves, in a vertical position like books on a shelf. By storing vertically, you put the weight on the hub rather than the tape edges. Horizontal storage can damage the tape edges, especially if the tape was not wound smoothly. 

Environmental changes can have negative effects on magnetic tape. This especially can be the case when you are moving tapes from one area to the other. If you have tapes in your car in the winter, and bring them inside to a warmer area, condensation will form on the tape. This is not a major problem as long as you do not try to use the tape while it is acclimating to the new environment. The video machines also have the same characteristics. If you bring your camcorder in out of the cold, let it warm up to ambient temperature before using it. Many video machines have a "DEW" error indicator, meaning moisture has condensed inside the machine and the machine is locked, preventing you from using it until it dries out.  

Moral: let tapes adjust to the new environment before using them. A few hours is the minimum for a significant difference. Longer is better. Government agencies allow a full day for tapes to acclimate. Don't force things by trying to warm the tapes with a heat source. 

Remember the tape substrate (backing) is plastic. In cold weather this plastic stiffens. Try to avoid using a cold tape. Doing so will greatly increase wear. If you can, keep the tape inside your coat close to your body so it gets some small amount of heat. Video or audio tape, same thing.  

While we're on the topic of tape care, remember heat is bad also. 80 degrees F isn't lethal, but tapes stored in a hot car at 120 degrees F almost certainly will have problems. Remember, vehicles can get a lot hotter than 120 degrees if in the sun. If you need to leave a tape in the car while you are working, well, that may be something you can't realistically avoid. But do not store tapes in the car, any time of the year.  

By the way, all of the preceding applies to digital audio or video tapes as well as analog. 

OK. Enough on tapes. What about the video recorder itself? 

Good question.  

Now that we know something about how to care for the tape, let's move on to the recorder. 

Video recorders also are miracles of modern technology. Just looking at a consumer VCR: here's a fancy piece of equipment, all the bells and whistles, high fidelity video, superb quality record and playback, remote control, timers, built in tuner for broadcast and cable, stereo audio, reliable, fairly rugged, capable of lasting several years even with junior operators in the house, and all for two hundred bucks. 

Some allegedly will even load and eject grilled cheese sandwiches. 

They work even when all crudded up with garbage rental tapes. Rental tapes, if you're not familiar, are rented by luddites whose VCR is underneath the television, on the floor, and full of cat hair. They shove these rental tapes into their machine, pollute them with garbage, then return them to the rental store where you rent and play them in your expensive, babied, high end VCR. We have three VCRs in our house, and an absolute rule is no rental or borrowed tapes in the two good machines. Only the crummiest one in the bedroom is allowed to load tapes which have been out in public, and when that machine croaks I will toss it in the dumpster with no regret. The bedroom machine is fifteen years old, in near-daily use, and works perfectly. 

Remember we discussed the composition of videotapes, and the magnetic coating is some composition largely made up of iron oxide. Another name for iron oxide is rust. These rust particles are abrasive. As the tape moves across the heads, the heads wear and the tape wears. Modern heads are made of very hard material, like ferrite, and sometimes the heads even are coated with a thin layer of glass or other substance which resists wear to the heads due to its hardness and minimizes tape wear due to its smoothness.   

But oxide still flakes off the tape. As the tape flexes from use, as tapes are used past their recommended lifetime, as temperature extremes affect the flexibility of the substrate and strength of the adhesive used to bind the oxide, more and more of the stuff falls off the tape and builds up inside the machine.  

Further, as tape machines are used, the metal parts in the transport become magnetized, which further attracts the magnetic oxide to the metal components. The parts which become magnetized are those in most intimate contact with the tape, and it is an unfortunate coincidence that those same parts are the ones which attract the abrasive iron oxide.  

So now we get into head cleaning.  Brown soap and a scrub brush, right? 

Lice shampoo? 

No. 

Head cleaning tapes?  

Probably no. 

Most head cleaning tapes work on the same principle as sandpaper does on wood. Dry tapes are the worst, although none of them are wonderful. 

The tape heads become encrusted with iron oxide from the tape, tape dust from manufacturing and wear, dust from the environment, smoke particles, animal dander, and all the pollution present in the environment. All this garbage mixes with tape lubricant or lubricant from the machine's mechanics, as well as grime in the air. The result is a thick, gooey substance which dries over a period of time into hard black sticky stuff that looks like tar. The longer it sits the more difficult it is to remove. Remember, there's nothing sealing the sensitive innards of the tape transport away from the environment. Poor housekeeping or smoking around a tape machine probably cuts head life in half.  

Dry head cleaning tapes merely scrub the tape heads, hopefully removing only the contaminant and not the head material itself. Avoid these where possible. 

Wet head cleaners use isopropyl alcohol, or Freon TF (preferred). You apply this solvent to the cleaning tape, then run them in the machine. Theoretically, the solvent dissolves contaminants on the head, then they are carried away by the cleaning tape. This is not a bad idea, and if you are lucky this may be what happens. Many times however, contamination on the heads is too aggressive to volunteer to jump off so easily. 

If you are using a solvent, keep the solvent bottle capped whenever you are not using it. Do not leave the tops off even for a minute. Alcohol evaporates as well as attracts water, and you do not want to apply water to the tape heads. Freon evaporates almost instantly, making it difficult even to apply it to the head cleaner. 

Do not open a large virgin bottle of alcohol and dip swabs or tools into the bottle. Rather, pour a small amount out into a separate container and dip into that, so you do not pollute the whole container. Discard the unused portion. 

The only people who really like head cleaning tapes are technicians who charge to replace damaged heads.  

Use head cleaning tapes only when necessary, only in emergencies when you actually see snow in the picture and not as a preventive maintenance tool. Use of head cleaning tapes results in accelerated head wear, so use them only when the picture becomes degraded. 

There is one head cleaning tool I do recommend for nontechnical users. It is sold by Radio Shack amongst others, and consists of some mechanical brushes which actually move back and forth on the surface of the head. You first wet the brushes with an appropriate solvent, then immediately (before the solvent evaporates) insert the tape into the machine and hit Record. Let the thing run for perhaps 30 seconds, then eject. Once I was bored and had an old junker Zenith VCR in the shop we used only as a tape rewinder. I pulled the head and looked at it under a potent magnifier I use for precision soldering. There was no really noticeable wear. I popped the head back in and ran the mechanical cleaning gadget most of an afternoon, pulling it every so often to dribble more alcohol onto the pads. After about 2 hours the cleaning cassette fell apart and I pulled the heads again and inspected them. There was some obvious wear, but nowhere near the significant wear I have seen from using head cleaning tapes. 

Anything you do use for cleaning should be replaced frequently. Otherwise you are just spreading crud previously removed back onto the heads. 

So what is the proper way to clean video heads? 

With the video machine unplugged, remove the top cover so you can see the insides. You will see a chrome-looking drum like a small hockey puck, usually set at an angle. This is the video head, and yes, it spins. Be very careful dealing with the head. Do not touch the polished edges with your fingers, or any other part of your anatomy.  

Obtain some lintless paper. Industrial, scientific or medical facilities will have them, many times under the brand name Kimwipes. A single box will last a lifetime, so see if you can appropriate a box. Do not use paper towels or other household stuff. You'll be worse off. 

Fold the paper until it is a half inch wide. Dampen it with solvent (alcohol, or preferably Freon TF, both obtained from Radio Shack). Get the paper wet but not dripping. You do not want the solvent dripping off into bearings or wherever and dissolving lubrication. 

Hold this wet paper against the side of the drum. Again, do not touch the polished edge of the drum with your fingers. Going to the top side of the drum, rotate it many times while holding the wet cleaning paper against the polished surface. I find it easiest to use the eraser end of a pencil as a tool to rotate the drum. Hold the cleaning paper firmly against the head, but not too hard. 

Take a look at the cleaning paper. You might even see black marks on the paper. Clean as described several times, or repeat until no more black comes off. Now the video heads are clean.  

Do not rub up and down against the video head or you get to buy a new one.  

There are other stationary heads in a video machine. These are the audio head(s) and the erase head. Look at everything in the tape path and clean it, using separate cleaning material for each component. You can wipe them without damaging them. Just remember not to rub the video heads  just hold against the chrome looking hockey puck, and spin. 

Also in the tape path is the capstan and pinch roller. The capstan is a small diameter metal shaft, and the pinch roller is a black rubber drum. The capstan pulls the tape through the transport, and its speed is precisely controlled to, in turn, control the speed of the tape moving across the heads. The tape literally is "pinched" between the capstan and the pinch roller. 

Clean these two items with solvent and cleaning paper. The rubber pinch roller gets sticky with tape grunge and likes to grab tapes. In either an audio machine or video machine, if it "eats" tapes, the capstan and pinch roller likely are dirty. With the cleaning paper, rub and rub until the amount of black coming off is less and less. Some always will be coming off as the roller itself is made of black rubber. 

Don't go overboard with cleaning solvent to where it drips down into bearings and dissolves lubricants. Do not use Kleenex or Q Tips as cleaning media. Fuzz comes off and plugs the heads, causing the very problems you are trying to prevent. 

Your machine is now cleaned. It will work better, last longer and you have saved some money. 

Tape Head Demagnetizing 

Tape heads need additional maintenance for best quality recordings. 

Tape machine heads, record or playback, eventually pick up some residual magnetism. Constantly moving magnetic tape will impart some sort of magnetism to the heads. Remember the tape is coated with magnetized iron oxide. 

Tapes recorded at higher levels will greatly speed up the problem. Video tends to be recorded fairly loud. 

In some cases, switching power to the machine on and off while it is recording will cause a transient to pop into the head, and create a monster instantaneous magnetic surge which is very effective at magnetizing the heads. The earth's magnetic field also contributes some magnetism. 

All heads in all machines sooner or later will become magnetized. 

Magnetized heads act like an eraser. They act exactly like a small magnet in intimate contact with the tape. Remember tape is magnetic media, and magnetic fields will erase it. The more times the tape is transported across the magnetized heads, the more it will be erased.  

The high frequencies are the first to go, for technical reasons. Hysterisis and tape characteristics mean the high frequency signals are weaker than lower ones, which is a reason for tape bias. 

When high frequencies go, audio on the tape will start to sound muffled. In human speech, the power is in the lower frequencies, but the intelligence is in the high frequencies. Therefore magnetized heads erase the intelligence but leave the power. This makes for muffled audio. 

Video response suffers more than audio. Your eyes can see problems in video before your ears can hear it in the audio. High frequencies in video are the detail, contrast and color. You first will notice the picture losing sharpness, losing contrast and color looking washed out. All these are symptoms of magnetized heads. 

If you notice this happening, you should stop immediately as every pass of the tape erases it more and more. The best audio forensics will not recover magnetic impulses which have been erased off the tape. 

Another term for heads being magnetized is "gauss". Gauss is a measure of the strength of a magnetic field, and the term is used to refer to heads with a magnetic field. 

The solution is to demagnetize, or degauss all tape heads in all magnetic media transports on a regular, preventive, basis. 

A degausser is a coil and core, with the core usually coming out to a point to concentrate the field and let you focus it accurately. An AC field is applied to the coil, such field usually being generated by 60 cycle mains power. The field builds up positive, then negative, 60 times a second. To degauss, you turn on the degausser while keeping it several feet from the equipment to be degaussed. At the moment you turn the degausser on or off, a large surge is generated which instantly can magnetize metal in close proximity. If a momentary switch, be sure to keep it pushed. 

Turn power off to the machine you are degaussing. The strong magnetic field will create a very loud hum which could be dangerous to the electronics if the system is on. 

While the degausser is active, and still keeping it several feet from the equipment, move the degausser in large (6 inches maybe) circles being careful not to reverse the direction. 

Move the degausser closer and closer to the heads, slowly, while reducing the diameter of the circles down to perhaps half an inch. Slowly approach the heads, keeping the degausser moving and not changing direction. Circle the heads, capstan and any other potentially ferrous components in thetape path. 

Make circles for perhaps 30 seconds. Do not at any point allow power to drop to the degausser. 

After 30 seconds, back the degausser away, keeping circles in the same direction but becoming larger as you back away.  

Back the degausser away to the full length of the power cord, several feet at least, before turning it off. 

You've now degaussed the heads and other metal parts in the vicinity. 

You created an increasingly stronger magnetic field varying in polarity. When you were close, you were strongly magnetizing the heads, but in opposite polarities, 60 times a second. When you backed the degausser off, you were decreasing the strength of the field very slowly, so the magnetic reversals got weaker and weaker, until hopefully the field strength (gauss) was down to zero and the heads were demagnetized. 

It is a good idea to do this often. You can't overdo it. I would suggest monthly at worst for intermittent duty, weekly for machines in daily use, and before every use for critical  machines used infrequently like tape editing setups. I realize, however, that this maintenance is far beyond the abilities and interest of most users. I included it here in the interest of completeness and so you appreciate even more the need for professional maintenance on your valuable equipment. 

The intelligence community making critical data recordings of satellite imagery downlinks cleans and degausses heads on instrumentation tape recorders before every reel of tape is hung. 

Prevention is the key. Once heads are magnetized, they are erasing your media.  

For audio cassette tape, there are degaussing cassettes available. These have an electronic circuit built in and some tiny batteries, all in a cassette shell. These use a much higher magnetic frequency of several kilocycles, and electronically decrease the strength of the field. They work well, take only a few seconds, and are convenient enough to use daily in dispatch center tape loggers, for example. I have not seen these for video cassette machines though. 

Erasing a magnetic tape uses a process identical to that described above, except the tape itself, rather than the head, is erased. Tape degaussers tend to have large magnetic cores rather than a pointed one for small items. Demagnetize the tape as above, making sure not to turn power on or off to the degausser unless the thing is several feet away from the tape and anything else which might be magnetized by the surge. 

And do not reverse the direction of the circles you are making. 

While most tape recording mechanisms erase the tape electronically before they record, doing it yourself manually will give you a quieter tape, with a better signal to noise ratio and cleaner, crisper video and audio. Cheap and simple and effective. Be a hero. 

Magnetic tape and transport care is a specialty field unto itself. Proper head cleaning and degaussing will result in much higher quality and more reliable operation. 

A real life story: How video could have saved the day 

Let's look at a real life story of what happens when maintenance on a video system is ignored. 

Recently in a major metropolitan area, a commuter train was equipped with video  cameras and recorders. There was an accusation that a Grayhound Bus had tried to beat the train across an intersection, didn't, and struck the train. 

There were perhaps a dozen people on the train according to employee testimony and fare analysis. 

Many more people than that filed medical injury claims against the city. 

Each car on the train had two video cameras and two video recorders. The city's defense attorneys hoped the video would show the number and identities of the persons on the car, and how severe the accident appeared. 

So far so good. This is one of the reasons you do video.  

In this particular case, only one car on the train was open to passengers at the time of the incident. This conveniently narrowed down the video. 

So what happens? 

The attorneys take the original tapes from the car in question. No one bothers to break the write protect tabs. 

They play them over and over again trying to see what had happened. There is about a 30 second window on one where critical events would make or break their case. No one can make anything of it, so they start sending this tape all around, hoping someone will get lucky and catch something someone else didn't. They're all playing this original tape with critical information on their home VCRs (remember the cat hair). 

A year later, and just a matter of weeks before the first court date, the city's attorneys and investigators decide the quality and detail of the video is not acceptable, and without the video they have no defense. They need someone to work with the video and bail them out. 

They call the kid. 

By the time I get the original videotape, it has been played so many times there is virtually no oxide left on the tape. The tape has been scrubbed clean, and I can just about see light through the tape at that point.  

Scratch using this thing as evidence. 

Earlier and later in the tape, the camera is way out of focus, and badly misaligned. The iris on the lens is open too much, making what is there way too bright and washed out to see. 

Forget it as evidence.  

The time/date on the video recorder either never had been set or was defective, because the time and date indicated were very different from the actual time of the incident. 

No way will this hold up as evidence. 

The quality of the video on the tape was horrible. Many dropouts, loss of sync, very poor high frequency response (little detail). Lousy contrast. All this is indicative of a machine badly in need of cleaning. 

Can't use this tape. Doesn't matter how desperate you are. 

The incident allegedly occurred on a date in August. There was a handwritten note on the tape that it had been placed into service in April of the year previous, when the video system originally was installed. The tape had been in continuous daily use for sixteen months. The tape was past worn. No forensic expert on the planet could have recovered anything useful from the video at this point. 

Turns out, the city had bought low bid. I knew this to be the case before even asking. They put out a spec written by a beancounter who had no knowledge of video, and who merely copied some information from a consumer catalog. Nothing called for a level of performance, only for a certain generic slate of equipment to be installed. Nothing called for an inspection by a video professional for proper performance. Nothing called for periodic inspection and maintenance. 

The city bought low bid. They thought that was the way to get the most for their money. 

The city so far has paid out high six figures to several persons who very likely were not even on the train at the time of the accident. The litigation likely will go on for years. 

The city still has not cleaned up the video systems on the train. We put in a proposal to inspect all equipment, bring it up to an acceptable level of performance, and perform quarterly inspections to ensure continued operation. Our proposal was not accepted because our price was too high. They didn't learn. 

The moral of the story? Several: 

     1)   Buy something decent to start. If you buy low bid, or even lowest price for the      same item, you had better do your homework and be an expert in the product.      Why is someone cheaper? Because they're operating at a lower profit margin?      Unlikely. Because they are leaving out something you aren't aware of? Far more      likely. Whatever the reason, you want to know. 

     2)   Budget a reasonable amount up front for maintenance. Don't ignore it now and  hope you can get it in next year's budget. Maintenance is a necessary, not an optional, operating expense. The "don't fix it unless it's broke" philosophy does  not work here. Just because things are working OK now does not mean you can  ignore maintenance. Have an intelligent and competent person write the preventive maintenance schedule. Keep written records of the work, in case you  need to prove due diligence in the future. 

     3)  Have an independent, competent person inspect the final job to be sure it meets or exceeds specifications. Keep a written record of the inspection. 

     4)   Test things frequently. 

     5)   Replace magnetic media frequently, on a schedule, and have this schedule in      writing. See below for more discussion on the life of magnetic tape. 

     6)   If something does happen you hope is caught on video, preserve the evidence. Break out the write protect tab on the tape. Immediately secure the original machine which recorded the tape, and save it for the forensics guys. Do not use the machine or do anything to it that will result in additional wear or possible damage. Have a competent lab make several realtime copies of the tape, then seal the original in safe storage. Do all processing and review with copies, not the original. Wear on the original cannot be restored. Wear on copies is not a problem; you just make more copies from the original. Have several responsible persons present initial the original tape, then seal it in an envelope. Make careful notes as to what is on the tape, time, counters, etc. Keep the tape in a standard chain of custody to avoid any challenges later if things go to court. 

     7)   Use common sense. Use clean, well maintained, professional equipment for your video work. Do not use home or consumer equipment. Using improper equipment is not being clever and saving money, it's being ignorant. 

     8)   Keep the time/date adjustment set properly on all equipment. Check it especially in spring and fall after time changes. Check also at year end. 

What is timelapse video?
Timelapse video is a method of using a single video cassette to record for longer periods than the standard 6 hours we get on our home VCRs. 

A standard VCR tape, like you would use at home, can record for 6 hours at the slowest (EP) speed. There are 8 hour tapes, but these are thinner in order to fit a longer tape into the same size cassette. Being thinner, they are more delicate and I emphatically do not recommend them for any serious purpose. The 6 hour tape in a popular brand of timelapse recorder can hold up to 720 hours, or one month, of video, on a single cassette. Neet. What's the story? 

Ordinary video, such as you watch on television, is actually a series of rapidly moving still pictures. Movies are the same thing. For standard video, you actually are seeing 30 frames per second. A frame is a complete picture.  Each frame is composed of two fields, an odd and an even field. Video is measured in lines, meaning the picture is written by a zigzag beam tracing back and forth across the screen. Broadcast quality video (average quality, by today's standards) is 525 lines. That means the beam sweeps across the screen, from top to bottom, 525 times to form one frame of video. 

In the early days of television, when electronics were not as refined as today, writing 525 lines was an expensive, complicated undertaking. So, the one frame of video (in the U.S.; other countries have different standards) was broken down into two fields. Each field is one half the picture. There is an odd field, and an even field. The odd field writes lines 1,3,5,7 etc. to a total of 262

video spying