Reversing Polarity On a Television...?

[DISLEX]

Und3ertak3r, Thank you. That is the sorta info I was looking for.

[roswell1329]

In a more security focused vein, it's interesting to note here that the signal "leaks" that Und3ertak3r speaks of are not the only leaks coming from your TV. Your TV also emits electromagnetic radiation which can be captured and translated using special equipment. The theory dates back to the 1950's when the military was concerned about electomagnetic radiation leakage and how to prevent it (the project was eventually named TEMPEST for Transient Electromagnetic Pulse Emanation Standard), but it was Dr. Wim van Eck who first theorized a practical way to harness and decipher these emanations into usable information. It is now possible to recreate the images displayed on computer monitors and television sets from a limited distance away. In this way, a television could be called a "transmitter" of EM radiation. Then again, by this standard, you could also call your blender, fax machine, photo-copier, and hair dryer "transmitters".

[Daedalus2100]

the thing has a cathode ray tube, this is what shoots the electrons and this cant be reversed

[firestarter5]

"Your TV also emits electromagnetic radiation which can be captured and translated using special equipment."

So technically, this could also be used on a computer monitor. But one question. This equipment that captures this radiation, is it capturing bits and pieces, or is it capturing a continuous flow? In simple terms, would they see a "screen shot" or "live continuous coverage"?

[shtychkn]

Does this mean I can't use my digital camera as a projecter??
Damn.

[Und3ertak3r]

thanks roswell1329

Your TV also emits electromagnetic radiation which can be captured and translated using special equipment.

now that I had missed.. thanks for the info.. more research for me..

Cheers

[DISLEX]

Good to see some good info comming out of my post!

[the_JinX]

He propably meant the polarity on the CRT ( Cathode Ray Tube ) well to bad.. it just wouldn't work..

read some more before comming up with stupid ideas !!

http://electronics.howstuffworks.com/tv.htm

[Und3ertak3r]

You know I have often wondered about measuring the Anode current on a tv pix tube, amplifing it and subtracting the incoming video from it.. and see what sort of image would result.. theory.. the phosphor on the inside front of the tube is excited by the electrons and releases photons, incoming photons Could have an effect on the generation of mor photons and therfore increase the Current progressing to the Anode of the Pix tube..

yes I know it sounds hairbrained..

Certainly easier to use a speaker as a microphone.. but certainly not while it is being used as a speaker..


Cheers

[slarty]

Not quite...

To the best of my knowledge, early TV cameras (before the invention of CCDs) used CRTs to produce the signal. Essentially it's like a television, but backwards. The CRT is scanned just like a TV, but the amount of light falling on a given part affects the current, this current change is then amplified, modulated etc, and transmitted.

However, an unmodified TV would definitely not do this

1. It probably isn't the right sort of CRT. A colour one wouldn't work for starters.
2. It has no lens, so at best it would only be able to tell how bright your room was

So theoretically if you modified a small black-and-white telly a bit, stuck an absolutely huge lens on the front (a good distance from the screen) and hooked it up to the appropriate electronics, you could make it into a camera.

All this was superceded by the invention of the CCD, a chip which produces electrical signals based on the light falling on it. This lead to the invention of video cameras, and TV cameras adopted them once the quality became good enough. These days they're so good that digital stills cameras can compete with professional-quality film. Also opened up the door for tiny (1cm cube or less) cameras used for security, espionage and gimmicks in mobile phones.