Mechanical video disc

[holtzman]

Amazing piece of dead technology which I found:
[url]http://www.youtube.com/watch?v=DuLj_lE_uJM[[/url]

http://en.wikipedia.org/wiki/Television_Electronic_Disc
It's mechanical!!!
Having started by Baird television, I'm now looking for other dead technologies and find them NOT LESS interesting than those widespread and succesfull ones. It's exciting to see tech evolution's dead branches and to investigate WHY they are dead

[Klaas Robers]

Volker, in 1971 or 1972 I have seen the Teldec mechanical video disc player here at Philips Research. Although it was amazing that it worked I still know that the pictures were remarkably unsharp. Teldec used a system that they called "TriPAL" to encode the colour. As far as we knew it was just line sequential RGB and with delay lines the not actual colours were retrieved. This made the definition in vertical direction 3x worse than Black and White TV. Telefunken had been in the devellopment of PAL-TV so they knew quite some tricks with these delay lines.

I remember too that the Teldec discs were very sensitive to dust. I was claimed that they could be played 1000 times, but then only in a dust free environment. In the You Tube film you see the dust particles as blemishes on the lines appearing and disappearing.

At the same time my Philips collegues were develloping the optical video disc, later known as Video Long Play VLP, later Laser Vision (LV), never became a success. From that derived is the CD, same optical technology. Needless to say something about CD.

[holtzman]

Klaas, you seem to be familiar with this technology... I would much appreciate sharing some of your knowledge!
Is it frequency modulated video signal? At least the grooves look like this. How is it possible to make a FM video? How audio is recorded?
How did they manage to make a master disc?! On what material? I think even about mastering at low speed, far low than playback. Otherwise the cutter must go too hot.

What surprises me so much, the fact that such inferior system made it to the market and the amount of investments the companies were ready to put on it.

[Klaas Robers]

yes of course the video is FM modulated. Base band recording always has huge problems with non linearity.

The play back was done by a kind of skate with a sharp back edge. The plastic is compressed by the skate and suddenly released by the sharp edge of the end. It then expands and this gave a HF variation in the pressure of the skate on the disc. After each play back the back-edge of the skate is grinded, that is the noise that you hear just after play back stopped.

I don't know how the master is made, but I guess just like e grammophone record master.

At that moment there was a struggle between companies on the system that could make it. There were several competitors:
- AEG-Telefunken with their mechanical Teldec
- Philips with the optical VLP, size and thickness like LP record
- Thomson CSF with also an optical foil disc
- Toshiba (?) with a capacitively read disc

There is always a heavy preassure to bring something to the market as soon as possible. At least something is happening then. I still know that the Philips management were not at all happy that Teldec was selling something.

In the same time the VCR was developed. The hope was that VCR (like audio compact cassette) and Video Disc (like grammophone disc) could start to live their own life next to each other. Philips was also in VCR with the VCR1500, the VCR1700, V2000, so betting on two horses.