On Sat, 8 Jan 2011 18:19:07 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:

mm wrote:
For 60 years, USA tv signals and European ones, etc. were not
compatible.

Sort of. Multisystem TV's Were common in the 1980's. There were only 4 systems
of video, although there there were lots of ways to transmit them.

They were NTSC (60Hz, 3.57mHz color carrier), 50Hz PAL, 60Hz PAL, and 50Hz
SECAM. There also was 405 line UK TV (dropped in the early 1980's) and
NTSC 4.43 (same signal, color carrier moved to make cheaper playback equipment).

I still have a 1985 Sharp TV set that will play both NTSC versions, All PAL
versions, and SECAM from anywhere except France. I had a 14 system VCR that
would play and record French SECAM and a different TV set to play it on.

My kids use a 21 inch 4:3 CRT that is simialr, except that it does not
have a French tuner. It added component and S-video instead.

Did they make digital tvs compatible from the US to Europe to Asia to
Australia, etc?

I also have had VCRS that included digital TV standards converters. They
were multisystem VCRs with the conversion feature added on top.

But digital TV was not needed, analog TV's played the signals fine. It was
just a matter of adding the correct hardware.

I think they should have. If not, is it only the 50 versus 60
vertical scan rate that was the problem?

The color carrier. NTSC used a phase modulated color carrier at 3.5mHz. PAL
used a similar carrier at 4.43mHz.

But thoss were in the analog signals. When they went to digital, why
didn't they stop using PAL or stop using NTSC? That is my point.

What tied them to both PAL and ntsc at the same time?

Regional pride?

Or was it because they wanted current analog tvs to be able to receive
digital signals that went through a set-top digital to analog
converter, and some tvs wanted 50 cycle and others 60 cycle, so if the
air-borne signal was the same, it couldnt' be converted to one of 50
or 60?


To fix a problem noticed in NTSC signals
the BBC adopted the practice (which was in the proposed NTSC spec but
dropped to save money) of alternating the phase every other line, hence
the name PAL (Phase Alternating Line).

TV sets which would lock on 50Hz or 60Hz signals as appropriate were not
a technical issue and by 1980 almost all made would anyway.

SECAM used a different decoding method, but those chips were easily found,
and it was common to see TV sets and VCRS that would play/record SECAM signals
broadcast using PAL over the air standards. Eastern Europe (Warsaw Pact
countries), most Arab countires, China, and the USSR used some form of SECAM
encoded signals with PAL frequencies.

The French used a different channel spacing, and AM sound, which made
their SECAM signals impossible to tune with the correct tuner. It also made
Eastern European TVs worthless in France and vice versa.

I don't think I've read anything about this.

You either must have head your head under a rock, or live in the US and never
traveled out of there.

Please see my question higher up.

Note that I had several multisystem TV sets, VCRS (BETA and VHS), and even
a portable combination AM/FM/SW receiver and TV set that looked like a
Star Treck tri-corder, all puchased in the 1980's in Philly.

Geoff.