26 May
2010
26 May
'10
11:58 a.m.
On 25 May 2010 at 17:15, Eric Smith wrote:
I believe a few test transmissions occured. The sets were never sold to
the general public, but Murphy (IIRC) made a few experimental ones, one
of which still exists somwehre.
The 405 line standard ('System A') was used for monochrome TV until the
early 1980s. When the 625 line standard was introduced in the late 1960s,
it was for one station (BBC2) only. Sets were so-called 'dual standard'
meaning they had a user control to slect between 405 or 625 lines. Since
there were quite a few differences other than just the line freuquency,
this control (the 'system swtich' was connected to many parts of the set.
Early colour sets were dual standard too, although the colour decoder was
disabled on 405 lines.
After a time, the 405 line trasnmissions were duplicated on 625 lines too
(although the 405 line signals contineud for the benefit of people who
had such sets).
While there exist other unofficial NTSC-related
systems such as the
so-called "NTSC-J" and "NTSC 4.43", these are NOT part of the NTSC
standard. While it is possible to use NTSC-compatible color encoding
with different scanning parameters, the result is *not* NTSC.
Didn't Britain briefly experiment with a 405/25 version of NTSC? I recall seeing a 405 line BW broadcast during a trip to
England in the
70s and thought it was the worst picture I'd ever seen since my
family's 9" Philco set. The frame rate was quite visible to my eye.
The frame rate (50 Hz) is the same aas on UK/European 625 line set, of
course.
I didn't find a correctly set-up 405 line set to be all that bad. A badly
set-up one, well....
-tony