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There is no easy way to tell by just examining the monitor visually. Even those with only a 9 pin rather than a 15 pin connector are sometimes SVGA (e.g., Mitsubisthi AUM1381 and NEC Multisync II which will do 800x600 at 56 Hz V non-interlaced and 1024x768 interlaced at 43 Hz V). You cannot even safety test scan rates on all monitors - some (mostly older ones) will blow up or be damaged by being driven with incorrect video. For a monitor that you already have, posting the model number or looking it up is really the only way to be sure of its capabilities. Quicky tests: 1. Check the video connector. If it has a high density (VGA) 15 pin connector then there is a greater likelihood of SVGA but not always. 2. Check the manufacturing date on the back. If it has a manufacturing date of 1991 or later, the likelihood of it supporting SVGA is higher as demand for VGA-only monitors was rapidly declining by this point. 3. Check the dot pitch on the CRT by examining the screen with a magnifier. If it is really coarse, the monitor probably cannot do anything beyond VGA. 4. Become familier with the major manufacturers and models so that you will recognize the common SVGA models. While not conclusive, positive results on the first 3 of these tests definitely increases the likelihood that it supports at least some SVGA modes. Of course, if you recognize a model number, you have dramatically increased your odds of success - assuming it works! The following URLs provide quick access to the general specifications of many common PC and MAC compatible video monitors: http://www.nashville.net/~griffin/monitor.html http://www.hercules.com/monitors/mdb.htm http://hawks.ha.md.us/hardware/monitor.html http://www.mindspring.com/~nunez/info/monitors/ (From: Adrian Kwong (a.kwong@ieee.ca)). Most new monitors employ frequency protection. The symptom that you will typically see is, a complete lack of video. Most monitors with multicolored power LED's, usually change color to indicate an error. Some monitors like Nokia's, will flash the screen on and off (black and white) to indicate that the over-frequency protection circuits have been activated. I have blown a few monitors by setting the video resolutions either too high, or setting the vertical refresh to something that puts the horizontal frequency waaay above the rated specifications. I actually have no idea how some of these monitors actually received a UL or CSA approval stamp, as I have seen some of these monitors catch on fire. Most of the 'blow outs', were just capacitors that exploded and about a room full of smoke fills the vicinity. All of the monitors that I blew up, were really old monitors with no frequency protection.
The sad fact is that even if you can obtain a new CRT you won't have the proper set up for getting proper alignment and convergence. They generally use various permanent magnet glued to the perimeter of the yoke to set the geometry of the raster. It takes a special factory jig to do this step or really great persistence and patience. However, if you have the time and will resist punching a hole in the new CRT before you finish, by all means. Also, consider the cost of a new CRT may be more than half the cost of the monitor when it was new. Replacing a monochrome CRT is a snap in comparison. A better (or at least less stressful) approach is to locate a monitor that died due to a circuit problem and salvage the CRT including the yoke and all the other magical magnets and coils. (From: Andy Cuffe (baltimora@psu.edu)). I have found that most 15" monitors use compatible CRTs. I just put the CRT from an old Gateway2000 with analog controls into a nice 2 year old monitor. As long as the yokes and CRT sockets are similar it should work fine. Don't try to swap the yokes or you will never get it converged.
(The following is from: Marty). Most of the old tube type color TV sets used a shunt HV regulator tube, usually a 6BK4. If it failed, or some component in the HV circuit failed, the high voltage, normally 25KV, could go up to 35KV or more, causing some X-Ray leakage from the CRT. In the early 70s when news of this radiation scare was first announced, there was a public outcry to immediately fix the problem. The Feds hastily imposed a requirement on manufacturers of TV sets to somehow render a TV set "unwatchable" if the HV exceeded rated limits. The manufacturers first response was to follow the letter of the law and the first "HEW" circuit simply blanked the video when the HV exceeded a setpoint to make the set "unwatchable". It was quickly noticed that the HV was not turned off with this circuit and the CRT still could emit some radiation. Many TV sets with this feature were left on so the consumer could listen to the sound, so the feds tightened the requirement. By this time new TV sets were all solid state and some manufacturers experimented with HV shutdown circuits, but most of these circuits were poorly designed and not reliable. Zenith thought they had the answer by regulating the HV with a bank of 5 capacitors across the horizontal output transistor to "hold down" the HV to 25KV. If one capacitor opened, the HV would only rise about 2KV, not a dangerous situation. This wasn't good enough for the feds. The "fix" that Zenith finally came out with, was a "4 legged capacitor. Two legs were the emitter return for the horizontal output transistor, & two legs were the HV holddown capacitor (the equivalent value of the bank of 5 caps). This "fix" was accepted by HEW and millions of TVs were produced. It worked so well, that other manufacturers soon followed the lead (Magnavox, GE, etc.). Then the worst happened! The 4 legged monsters started failing in a large numbers. Not opening completely & not shorting out. They sometimes allowed the HV to skyrocket to over 50KV. Some of them even cut the necks off of the CRTs. Zenith issued a recall on those models with the problem (more than one entire model year). After several "improved" versions of the capacitor, the problem was fixed but that recall almost bankrupted the company. Other companies had failures too, but usually not as dramatic as Zenith's. Magnavox used the HV holddown capacitor, both single & 4 leg version in several 70s era TV sets and is a good candidate for fireworks as well.
This question comes up so often and it does sound like a neat project to give a defunct TV a second life. Don't expect to end up with a Tek 465 on the cheap when you are done. However, it could be a fun learning experience. CAUTION: See the safety recommendations below. You will be severely limited in the performance of such a scope. TVs and monitors are designed to operate at a very narrow range of horizontal scan rates and the high voltage is usually derived from the horizontal deflection. So, you would need to retain the original deflection system for this purpose at least. 1. You will need to disconnect the defection yoke from the horizontal and vertical deflection circuits of the TV or monitor without killing the HV. (also, doing all this without killing yourself as well). Depending on the design, this may be as simple as unplugging the yoke connector. More than likely, you will need to substitute a load for the horizontal deflection coil. A coil from another sacrificial similar TV or monitor would probably suffice. Warning: at this point you have a really bright spot in the middle of the screen which will turn to a really black spot if the brightness is not turned way down really really quickly. 2. For the horizontal, you need a ramped current source. You are driving a non-ideal inductor (the deflection coil) so it has both inductance and resistance. Thus the waveform is a trapezoid - a voltage ramp (for the resistive part) superimposed on a voltage step (for the inductive part). This should not be too difficult. Don't expect to be able to achieve really fast sweep. Even running at normal TV rates is non-trivial. 3. Similarly, for the vertical you need to drive with a voltage (your signal) controlled current source. However, if you just screwing around, then the linearity etc. for the vertical may not be that important. In this case, one way is to put a current sensing resistor in series with the deflection coil and use this in a power op amp type of feedback arrangement. (You could do this for (2) as well. 4. There is a good chance that the original brightness control will work as an intensity adjustment. However, with some TVs and monitors, this depends on receiving a valid video signal. You may need to improvise. If you do want to control the intensity from a signal source, you should be able to tap into the drive signals going to the little board on the neck of the CRT. 5. Don't expect high bandwidth, uniform response, or any of the other things you take for granted with a decent scope. That takes work. However, as a fun project, this certainly qualifies. Interchanging the functions of the horizontal and vertical deflection yoke (and rotating it 90 degrees) may provide a better match of horizontal and vertical bandwidth to your intended applications or experiments. 6. With a color TV or monitor, these experiments could be quite interesting and educational but there may be color fringing effects since you are not compensating for certain aspects of dynamic convergence at all. 7. SAFETY: Once you disconnect the deflection yoke from the TV or monitor's circuits, move the original circuits out of the way and put a barrier between between you and the rest of the TV or monitor. All you will need are connections to the deflection yoke on the CRT (unless you want to do intensity modulation in which case you will need to drive the video output(s) to the CRT cathodes. I would recommend against doing this if your unit is one of those with a totally 'live' chassis as there would be additional safety hazards and circuit complications).
I am not sure why anyone would really want to do this other than as an experiment - it would be interesting one. If a composite video signal is the input, you will need a sync separator. For VGA, the sync signals are already available. You will have to construct a vertical deflection voltage ramp generator which can be locked to your vertical sync signal. The horizontal timebase of the scope will be fine for the horizontal deflection and should easily lock to your horizontal sync pulse or (if the scope has a TV trigger mode) directly to the video signal. A video amplifier will be needed if your Z axis does not have an internal amplifier (you need .7 V p-p to be full brightness range.) Unless you provide automatic gain control, this will need to include offset (brightness) and gain (contrast) adjustments. Even if there is an internal amplifier, it may not have the required bandwidth for the video signal. However, the overall brightness may be disappointing - a scope is not designed for overall high brightness. The beam focus will not be as good as that on a little TV either.
The whole idea of stereo 3-D vision to put the left and right views to the appropriate eyeball. There are two common ways of doing this: 1. Use different colors for the two views with color filters in from of each eye to separate the views. This is what were often used for the really bad (content wise) sci-fi movies of the '50s. 2. Display alternate views on the same monitor screen but use LCD shutter glasses to allow each eye to only see the appropriate view. This requires increasing the refresh rate to avoid unacceptable flicker. The first approach can be used with any TV and a pair of monochrome video cameras. Of course, true color cannot be used since pure colored images are needed to separate the stereo views. Alternating views with synchronized LCD glasses is a possibility but and has been used commercially but requires special hardware to synchronize to the computer's video card. Best results are obtained with refresh rates of at least 120 Hz permitting 60 full left-right frames per second. If you try to this with a regular TV or CGA monitor, the resulting refresh rate would be 30 Hz with a 50% duty cycle which is likely to be useful only as a short experiment - else your viewers will likely develop splitting headaches.
(The following assumes a normal video card with a mini-DB15 VGA/SVGA
connector - if yours has BNC connectors, the improvement may be even
greater.)
The answer is an unqualified maybe. In principle, the BNC cable should have
higher bandwidth and better transmission line characteristics (impedance,
termination) and result in sharper crisper images with less ghosting,
ringing, and other artifacts. However, this will only likely be significant
at higher refresh rates (1024x768 at 75 Hz and beyond) and depending on your
monitor and video card, you may see no change - or it may even get worse. It
is best to purchase a good quality VGA to 5-BNC cable with a return privilage
and try it. I suggest a 5-BNC cable even if you only need 3 or 4 connectors
so that it will be compatible with any monitor or video card you might have
in the future. Cost should be in the $25 to $70 range.
Potential advantages of using the BNC connector inputs on your monitor
with a good quality cable are:
* higher video bandwidth -> sharper display.
* proper connectors (at one end, at least) and correct
termination -> less ghosting and ringing.
For a good monitor with a high quality video card, the difference can be
dramatic - as is the case with my ATI GPT and NEC 5FG.
(From Bob Myers (myers@fc.hp.com)).
However, one should also note that connecting via BNCs generally disables
monitor "plug 'n' play" features, since these are based on ID information
conveyed on dedicated pins (using the VESA DDC & EDID standards) on the
15-pin "VGA" connector.
As of last year, a new connector standard - the VESA Enhanced Video
Connector, or EVC - has been released, which will provide both greatly
improved video signal performance AND support for DDC and a number of
other features.
Most current monitors comply with the VESA Display Data Channel (DDC) standard
which provides a path and protocol for getting some basic ID information
(model, manufacturer, supported timings, chromaticites, etc.) back from the
monitor. Under that standard, the following new signals have been added to
the DB-15 connector:
Pin 9: +5 VDC from host
Pin 12: Serial data
Pin 15: Data clock
Pin 10 (the old sync return pin) now does double duty as the return/reference
for DDC. The DDC system uses the I2C spec for one level of implementation,
although a base level is also provided in which the data is clocked back
from the display by the vertical sync pulse.
The old 4-line ID scheme using pins 4, 11, 12, & 15 is obsolete. I can't
think of too many hosts, or ANY monitors, still using it.
Additional information on the EVC standard is available from the VESA web site,
http://www.vesa.org.
And one manufacturer's way around the preceeding:
(From: Russ Smith (smith@ur-guh.com)).
The Nanao F2-21 I'm using is connected via 5 split-out BNCs
on its end; on the OTHER end is the standard VGA connector - that
connector plugs into not the video card, but a little "black box"
which performs the plug-n-play identification. That little widget
plugs into the PnP-compatible video card (Matrox Millenium).
Thus, even though BNCs are used at the monitor end and the monitor
itself can't communicate anything useful, the information is
none-the-less communicated.
A hack that works.
This is straightforward, if time consuming and tedious.
The five coaxial cables (75 ohm, RG59 typical) are wired as shown in the
table. The corresponding VGA connector pin numbers are in ().
Coax Center Coax Shield
--------------------------------------
Red Video (1) Red Return (6)
Green Video (2) Green Return (7)
Blue Video (3) Blue Return (8)
H Sync (13) Ground (5,10)
V Sync (14) Ground (5,10)
Tie pin 11 (ID0) to Ground to indicate a color monitor.
Leave pin 12 (ID1) open.
Make sure that the lengths of the cables are fairly well matched - to within
a couple of inches - to assure that the 3 color channels line up precisely.
(One foot of cable is about 1.5 to 2 ns of delay which is significant for
a 10 ns dot clock!).
Also note (see the other sections on BNC cables) that you will lose your
Plug and Play capabilities without the direct control connections to the
monitor (or for monitors without these featuers).
That's it!
You will wish that your fingers were about 10 times smaller than they are,
however. :-)
These are nearly always fixed frequency monitors with a scan rate that is not compatible with typical SVGA cards. They may have a special connector like a 13W3 or 3, 4, or 5 BNC connectors. Some have a non-standard connector. While these normally use standard analog video signal levels, you have a couple of problems out of the starting gate: 1. The fixed scanning frequencies of most of these monitors are not directly compatible with typical SVGA standards. Many high end boards like the ATI ProTurbo can scan at 1280x1024 probably at an appropriate refresh (horizontal is going to be the critical one) rate. Also, boards that allow software adjustment of size (like the ATI) are in effect changing scan rates as well so that gives another degree or two of freedom. However, many typical video cards do not provide this degree of flexibility. 2. The monitor needs sync-on-green (3 BNC connectors), composite H and V sync (4 BNC connectors and 13W3) or at least a VGA to BNC adapter cable (5 BNC connectors). Your VGA card normally puts out separate syncs. Many video cards have a software mode (probably accessible in the setup program) to enable composite sync output so for these at least there is no problem with a 4 BNC monitor. You can build a circuit to generate the required video for a 3 BNC monitor if you are so inclined. See the "Sync on Green FAQ" for detailed information and schematics. 3. What you do for booting since the default will be VGA (at least for DOS/Windows. If you only use your PC at one fixed high resolution, than this may not be that much of a problem.. There are specialized boards that will emulate standard VGA/SVGA modes using a fixed frequency monitor. For more information, see the document: "Notes on Approaches to using Fixed Frequency Monitors on PCs".
Pulling a fixed frequency monitor by more than a few percent will likely be a problem. I know this is not the answer you were looking for but getting a new inexpensive video card may be a better solution. Other types of monitors - XGA for example - may be variable or multiple frequency but incompatible with VGA/SVGA. Some adjustment may be possible but how far you can go will depend on many factors. If not, you are looking for an adjustment called horizontal oscillator, horizontal frequency, or horizontal hold. If you do tweak, mark everything beforehand just in case you need to get back to the original settings. There is a slight risk of damage, particularly when lowering the horizontal rate as this increases peak current to the horizontal output transistor. This may result in immediate failure or more stress on components resulting in failure down the road. I have no idea with your monitor. An alternative that may be possible is to use the setup or install program that came with your video card to decrease horizontal size and then adjust vertical size if needed. This would best be done while monitoring with a scope or multiscan monitor. A byproduct of software adjustments to size will often be a change in the scan rate of a few percent which may completely cover what you need. The reason this may work is that these adjustments vary the length of the H and V video back-porch which affect the total scan time. I know I can do this with my ATI cards. Also see the document: "Approaches to Using Fixed Frequency or Non-Standard Monitors on PCs" which includes a specific modification to permit an IBM9517 XGA monitor to be used at VGA/SVGA scan rates.
My general recommendation is that if you have the space, buy an inexpensive
TV - the quality in the end may in fact be better. And, it will be usable
without tying up your expensive monitor and (maybe) PC.
Some older monitors like the Mitsubishi AUM1381 and Emerson CGA (which also
has a speaker) include a composite NTSC input jack requiring only a baseband
video source like a VCR. These do produce a very nice picture. However,
most newer auto-scan VGA/SVGA monitors do not go to low enough horizontal
scan rates. To display NTSC or PAL on these requires a scan convertor
(likely to be very expensive) or at least a scan doubler (less expensive
but not as good).
For the case of older monitors with digital (TTL) inputs, see the section:
"Modifying a CGA (or EGA) monitor for NTSC or PAL input".
You can also buy video input cards complete with tuners ('PCTV') which
will put TV into a window and allow you to idle away the time you are
supposed to be working while watching 'Mork and Mindy'.
While various convertors are advertized to use a computer monitor
with video from a VCR or other source, keep in mind that if it sounds
too good to be true, it probably is like the claim of a $200 box for this:
OK, let me get this straight - this card/box will enable a 31.4 KHz horizontal
scan rate monitor (VGA) be used as a TV - yes or no? It thus includes a video
A/D, full screen frame buffer, D/A, and all the other tuner stuff for under
$200? I don't think so. A scan doubler - which is a subset of the above -
will not result in a high quality picture since it will display pairs of
lines interleaved or leave alternate lines blanked reducing brightness. Or
does the impressive advertisement leave out the key requirement that the
monitor sync at the NTSC horizontal scan rate of 15.734 KHz (most newer
monitor do not)? Or is it a board that plugs into a PC and indeed does use
the resources of the PC including the VGA card and bus?
In any case, get a written money back satisfaction guarantee.
These are often high quality monitors and would make nice TV displays - especially as there are many no doubt gathering dust on their way to the dumpster! However, these are digital (TTL) monitors with respect to the video inputs and proper linear video amplifiers may not even be present. Therefore, you may need to implement both the NTSC or PAL decoding as well as boosting the signal levels to the hundred volts or so needed to drive the CRT. The scan rate of CGA is the same as NTSC so deflection is not a problem. For PAL (625/50) instead of NTSC, the vertical rate will need to be reduced to 50 Hz but this should not be a problem. The horizontal scan rate is close enough (15.625 KHz). Similar comments apply to EGA monitors that have a compatible scan rate. EGA represents a range of scan rates between 15.75 KHz and 21.85 KHz so this should not be a problem.
It is not possible to just connect monitors in parallel. The terminating resistors (75 ohms) of each monitor will also be in parallel reducing signal strength and resulting in various problems with cable termination including ghosting, ringing, etc. A simple circuit to implement a video splitter is shown at: http://www.anatekcorp.com/articles.htm This is just a set of emitter following buffer amplifiers and should suffice for many applications. Various companies including Elantec, Analog Devices, Maxim, and others have video amplifier chips as well but the basic approach may be adequate for your needs.
Assuming this means NTSC: 1. You need to convert RGB to NTSC - there are single chips for this. Try Sony, Philips, Motorola, and others. These will combine the R, G, B, H sync, and V sync into a single composite video signal using a minimum of additional components. 2. You need to match the scan rate to NTSC - 15.734 KHz horizontal. Even basic VGA is twice this - 31.4 KHz. If your video card can be programmed to put out interlaced NTSC rate video then this is easy. If not, it is more difficult. If you want to use anything higher res than VGA, it is a very non-trivial problem requiring the construction of a scan convertor which includes a video A/D, full frame store, interpolator/readout timing, video D/A. Unless you are an experienced digital/analog designer, you really do not want to tackle any of this. For the special case of VGA->NTSC, you may be able to get away with just storing a single scan line since the horizontal frequency is (almost) exactly twice the NTSC horizontal of 15.734 KHz. A double buffer where one buffer is storing while the other is reading out at approximately half the VGA pixel rate should work. With appropriate timing, even lines become the even field for NTSC and odd lines become the odd field (I may have this backwards). It is still not a trivial undertaking. Also, keep in mind that the quality you will get on NTSC will be poorer than the VGA due to fundamental NTSC bandwidth limitations. Also, flicker for line graphics will be significant due to the interlacing at 30 Hz. Even this is a non-trivial undertaking. The requirements for PAL are very similar. For 625 lines systems, the 800x600 is the format that most closely matches the TV resolution. You can also buy little boxes to do this. Quality is general not great as you are seriously limited by NTSC/PAL and the VCR. Except for presentations on existing TV rate equipment, it is probably not worth the effort. This is totally useless for any serious computer applications. For professional presentations, modern video projectors are available that use high resolution LCD panels and real-time scan conversion. However, they are quite expensive (up to $10,000!!!).
(From Bob Myers (myers@fc.hp.com)). The Kell factor - which has to do with the fact that we're often undersampling an image from the standpoint of the Gospel According to St. Nyquist - IS a factor in the reduction of vertical resolution, but interlacing plays a part as well. This comes from at least two factors: 1. The monitor or receiver usually cannot precisely interleave the two fields. 2. More importantly, there are steps taken to reduce the interline flicker which reduce the effective vertical resolution. This includes running the line width of the display somewhat larger than would otherwise be the case, and in interlaced cameras, discharging the entire screen (including the lines from the "other" field) after every field scanned. Interlace is particularly troublesome on moving images, where you will often perceive momentarily "missing" details. There was a LOT of discussion regarding the gory details of interlacing in the recent HDTV debates within SMPTE and other groups.
Talk about unusual. This was posted to sci.electronics: "Something VERY strange is happening, and I cant explain it. There is a "ghost" on my TV screen of the text appearing on my computer screen. They are NOT hooked together in any manner. They are about 4-5 feet apart. Although, the antenna cable runs within a foot of my computer. I am wondering what causes this to happen. I have experienced interference, but this is more like a wireless second monitor. I can turn off my monitor, and look over at the TV. The text on the TV is scrolling up every 9 seconds. (like when the v-hold isn't adjusted.) Any Ideas?" This is probably caused by RFI - radio frequency interference - from a CGA or PC TV card being picked up on the TV's cable or antenna. Only CGA has a scan rate that is nearly the same as NTSC. Any other PC video scan rate would result in a torn up or rolling picture.
Pack Rat Trick #457384 Next time you scrap a computer monitor (or tv), save the degaussing coil (coil of wire, usually wrapped in black tap or plastic) mounted around the front of the tube. To adapt it for degaussing sets, wrap it into a smaller coil, maybe 4"-6". To limit the current to something reasonable, put it in series with a light bulb (60-100W). You need AC current to degauss, so just put the bulb in series with the coil and use the your local 120V outlet. BE VERY CAREFUL that you actually wired it in series, and that everything is properly insulated before you plug it in (A fuse would be a real good idea too!!) A few circles over the affected area will usually do it. Note that it will also make your screen go crazy for a little bit, but this will fade out within a minute or so. Just a couple of points for emphasis: 1. The coil as removed from the TV is not designed for continuous operation across the line as indicated above. In fact, it will go up in a mass of smoke without the light bulb to limit the current. The poor TV from which this organ was salvaged included additional circuitry to ramp the current to 0 in a few seconds after power is turned on. 2. Reducing the coil size by a factor of 2 or 3 will increase the intensity of the magnetic field which is important since we are limiting the current with the light bulb to a value lower than the TV used. You don't need to unwind all the magnet wire, just bend the entire assembly into a smaller coil. Just make sure that the current is always flowing in the same direction (clockwise or counterclockwise) around the coil. 3. Insulate everything very thoroughly with electrical tape. A pushbutton momentary switch rated for 2 amps at 115 volts AC would be useful so that you do not need to depend on the wall plug to turn it on and off.
A couple of comments: first of all, it makes no difference whatsoever if the display is on while it's being degaussed. (Oh, some people DO like to watch the psychedelic light show, but it really doesn't help anything for it to be on.) Actually, there is a very minor case to be made for degaussing while OFF, at least for the Trinitron and similar tubes. (The field of an external degauss coil CAN cause the grille wires to move slightly, and they're a bit more flexible when hot - so it is conceivable, although certainly unlikely, that you're running a higher risk of causing the grille wires to touch or cross and become damaged.) Secondly, a good practice for degaussing is to slowly back away from the monitor after giving the screen a good going over. Once you're about 5-6' away, turn the coil so it's a right angles to the CRT faceplate (which minimizes the field the monitor is seeing), and THEN turn to coil off. This is to reduce the possibility of the field transient caused by switching the coil off from leaving you once again with a magnetized monitor. The last point is to make sure that you DON'T leave the coil on too long. These things are basically just big coils of wire with a line cord attached, and are not designed to be left on for extended periods of time - they can overheat. (I like the kind with the pushbutton "on" switch, which turns off as soon as I release the button. That way, I can never go off and leave the coil energized.) Oh, one more thing - make sure your wallet is in a safe place. You know all those credit cards and things with the nice magnetic stripe on them? :-) (Actually, I've got a good story about that last. I was teaching a group of field service engineers how to do this once, and being the Big Deal Out of Town Expert, made VERY sure to place my wallet on a shelf far away from the action. Unfortunately, Mr. Big Deal Out of Town Expert was staying in a hotel which used those neat little magnetic-card gadgets instead of a "real" key. Ever try to explain to a desk clerk how it was that, not only would your keycard NOT let you into your room, it was no longer anything that their system would even recognize as a key? :-))Go to [Next] segment
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