Dave Plowman (News) wrote:

But I don't think that's correct. For it to work, TV would have to be
mains locked. It was in the very early days, but later was pulse generator
locked with no direct reference to mains other than being nominally the
same frequency. Mains lock was really just to make receiver design simpler.

You sort of danced around it. In the very early days is when the frequency was
set. Once set it stayed.

That really was the point of my very long explanation. A long time ago someone
decided to fix the scan rate and representation of data. The actual information
used in all the TV systems was the same, it was just used with incompatable
frame rates, encoding systems and transmission systems mostly for politcal
reasons. TV sets that could receive, decode and play any and all signals
existed.

The reason that everyone did not have a universal TV set was because the price
was kept lower with single system sets and countries like the UK, which made
a substansial income from the TV license did not want you watching tv from
France or the Republic of Ireland for free.

From a technology point of view, it was obvious that the digitial TV standards
MPEG and so on were designed with existing TV sets in mind. If not they would
not have been a continuation of the old limited national standards with their
horrible color encoding choice (1/4 of the resolution that the monochrome
signal had) and instead gone with the more extensible, accurate and easily
compressable RGB system used in computer data.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Those who cannot remember the past are condemned to misquote it.