"Mark Carver" <mark.carver@invalid.invalid> wrote in message
news:j35rf0Fa39uU1@mid.individual.net...
> Up until the early 80s, your local ITV station would in the 10-15 seconds
> or so before cutting to the network programme
> adjust the phase of the master SPG such that it drifted into sync with
> the network feed. Normally done by adding or subtracting one line per
> field.
> This had a drawback, that during this period any VTR or Telecine machine
> servos would go bananas because they were receiving no standard syncs.
>
> That's why the introduction into the programme was either a camera shot of
> the announcer, or a caption (such as a clock)
>
> When Frame Store Synchronisers appeared in the 80s, the ITV companies
> adopted those, so whatever was stuffed into the input of a Frame Store
> would be locked on its output to the local sync. That also liberated the
> companies to be able use VT derived logos etc into programmes.

What technology did BBC use on programmes such as Nationwide when they were
switching network between feeds from various different regions during the
course of the programme? Everything had to be in sync at the vision mixing
centre (BBC TV Centre in Wood Lane or else Lime Grove) irrespective of the
fact that there would be a delay between the contributing regional studio
and the off air pictures that their region's transmitters were
broadcasting - equivalent to the round trip regional studio-TV
Centre-regional transmitter.

When ITV regions contributed programmes to ITV Network (eg Emmerdale Farm
from YTV followed by Crossroads from ATV followed by The Sweeney from Thames
[fictional schedule!]) did each region in turn playout its programme from
its own VT, or were the tapes sent to a central network playout centre? If
it was the former, how did they handle the synchronisation?

On 30/12/2021 16:05, NY wrote:
> "Mark Carver" <mark.carver@invalid.invalid> wrote in message
> news:j35rf0Fa39uU1@mid.individual.net...
>> Up until the early 80s, your local ITV station would in the 10-15
>> seconds or so before cutting to the network programme
>> adjust the phase  of the master SPG such that it drifted into sync
>> with the network feed. Normally done by adding or subtracting one
>> line per field.
>> This had a drawback, that during this period any VTR or Telecine
>> machine servos would go bananas because they were receiving no
>> standard syncs.
>>
>> That's why the introduction into the programme was either a camera
>> shot of the announcer, or a caption (such as a clock)
>>
>> When Frame Store Synchronisers appeared in the 80s, the ITV companies
>> adopted those, so whatever was stuffed into the input of a Frame
>> Store would be locked on its output to the local sync. That also
>> liberated the companies to be able use VT derived logos etc into
>> programmes.
>
> What technology did BBC use on programmes such as Nationwide when they
> were switching network between feeds from various different regions
> during the course of the programme? Everything had to be in sync at
> the vision mixing centre (BBC TV Centre in Wood Lane or else Lime
> Grove) irrespective of the fact that there would be a delay between
> the contributing regional studio and the off air pictures that their
> region's transmitters were broadcasting - equivalent to the round trip
> regional studio-TV Centre-regional transmitter.

The Beeb did the reverse technique to ITV's. Natlock, basically the
remote studio's SPG was sync'd to TV Centre or Lime Grove by using
remote control tones up a landline I think ?
>
> When ITV regions contributed programmes to ITV Network (eg Emmerdale
> Farm from YTV followed by Crossroads from ATV followed by The Sweeney
> from Thames [fictional schedule!]) did each region in turn playout its
> programme from its own VT, or were the tapes sent to a central network
> playout centre? If it was the former, how did they handle the
> synchronisation?

The originating production company usually played out their programme to
the network, so yes, you could have BT switching the network source
every 30 minutes some evenings.
Sometimes though for stuff that wasn't shown at the same time in all
regions, then some regions would record the programme, and timeshift it.
Sometimes they would part network.  I think for instance Southern would
record Crossroads playout from ATV at 6:30, to playout locally the next
day at 5:20, and at the same time feed that playout to the other ITV
companies that also showed Crossroads at 5:20.

Network movies were normally played out by one of the big five companies
(Thames, LWT, ATV, Granada, YTV)

It wasn't until the late 90s/early 00s that ITV's playout was
centralised to London

On 30/12/2021 11:28 am, NY wrote:
> "Adrian Caspersz" <email@here.invalid> wrote in message
> news:j35iclF8chfU1@mid.individual.net...
>> On 29/12/2021 17:42, Mark Carver wrote:
>>> On 24/12/2021 00:16, JNugent wrote:
>>>>
>>>>> Did film recording of a programme that had filmed inserts take any
>>>>> precautions to make sure that the change from one film frame to the
>>>>> next in the film recording occurred in sync with the film insert as
>>>>> it was originally telecined for the programme, rather than
>>>>> happening to be one field adrift?
>>>>
>>>> I seem to remember mention of "station sync", which meant that all
>>>> video being transmitted was locked to a station-wide time-signal,
>>>> presumably to avoid the problem of which you speak.
>>>
>>> It still is, it's the bedrock of all TV broadcast systems. Yes, it
>>> keeps f1 and f2 in step for all sources locked to it. Up until the
>>> mid to late 60s, not all vision mixers (the equipment, not the
>>> operators of the same name !) didn't always cut between sources
>>> during the vertical blanking interval, and you'd so the image 'slice'
>>> at the cut point
>>
>> Back long ago here in London in the 80s, it was entertaining watching
>> the sync lost and sound glitches, when they twice weekly switched
>> between the LWT and Thames companies that provided London ITV.
>
> I remember that - a picture that rolled or nudged, with coloured patches
> - like a bad VHS edit.
>
> Was there a fundamental reason why LWT and Thames couldn't synchronise
> their feeds to the ITV network, either by feeding from a shared clock
> source, or else by a suitable delay in the video (which is a lot easier
> once there is digital framestore technology to do this, instead of
> having to use a glass-block delay line). I presume the master clocks for
> Thames and LWT would be at Euston and at Teddington respectively, so
> there isn't much distance between them for signal propagation delays.

Euston and Teddington were both Thames establishments. LWT had the South
Bank studios and I think that for for a while, while waiting for
completion, the old Rediffusion studios at Wembley)
>
> I remember that the changeover was more visible on some TVs than others,
> depending on how long it took their line/frame sync oscillators to lock
> onto a slightly early/late sync pulse. VHS recordings tended to magnify
> the effect...

On Thu, 30 Dec 2021 13:45:04 +0000, Mark Carver
<mark.carver@invalid.invalid> wrote:

>On 30/12/2021 13:27, Scott wrote:
>> On Thu, 30 Dec 2021 11:10:13 +0000, Adrian Caspersz
>> <email@here.invalid> wrote:
>> [snip]
>>> Back long ago here in London in the 80s, it was entertaining watching
>>> the sync lost and sound glitches, when they twice weekly switched
>>> between the LWT and Thames companies that provided London ITV.
>> Why would this be any more of an issue than switching between local
>> and network programmes at the individual francises? Surely STV in
>> particular would have lot of switching to do and I don't recall this
>> being problematic.
>See my other post.
>
>As far as network programmes being in sync with local ITV company, that
>was quite a different arrangement
>
>Up until the early 80s, your local ITV station would in the 10-15
>seconds or so before cutting to the network programme
>adjust the phase  of the master SPG such that it drifted into sync with
>the network feed. Normally done by adding or subtracting one line per field.
>This had a drawback, that during this period any VTR or Telecine machine
>servos would go bananas because they were receiving no standard syncs.
>
>That's why the introduction into the programme was either a camera shot
>of the announcer, or a caption (such as a clock)
>
>When Frame Store Synchronisers appeared in the 80s, the ITV companies
>adopted those, so whatever was stuffed into the input of a Frame Store
>would be locked on its output to the local sync. That also liberated the
>companies to be able use VT derived logos etc into programmes.

I am definitely missing something here. If each franchisee could
insert its own adverts into a networked programme and return to the
programme on time, why would there be a difficulty in moving from one
company to another?

"JNugent" <jennings&co@fastmail.fm> wrote in message
news:j365sfFbve8U1@mid.individual.net...
> On 30/12/2021 11:28 am, NY wrote:
>> I presume the master clocks for Thames and LWT would be at Euston and at
>> Teddington respectively, so there isn't much distance between them for
>> signal propagation delays.
>
> Euston and Teddington were both Thames establishments. LWT had the South
> Bank studios and I think that for for a while, while waiting for
> completion, the old Rediffusion studios at Wembley)

Duh! Of course. I remember Magpie being advertised as coming from Teddington
Lock - they may have given that as a correspondence address. And Magpie was
weekdays not weekend.

That means that The South Bank Show (with the nasally snuffling voice of
Melvin Bragg) must have been a "weekend" programme if it was made by LWT
(where "weekend" includes Friday night).

"Mark Carver" <mark.carver@invalid.invalid> wrote in message
news:j365erFbvpvU1@mid.individual.net...
>> What technology did BBC use on programmes such as Nationwide when they
>> were switching network between feeds from various different regions
>> during the course of the programme? Everything had to be in sync at the
>> vision mixing centre (BBC TV Centre in Wood Lane or else Lime Grove)
>> irrespective of the fact that there would be a delay between the
>> contributing regional studio and the off air pictures that their region's
>> transmitters were broadcasting - equivalent to the round trip regional
>> studio-TV Centre-regional transmitter.
>
> The Beeb did the reverse technique to ITV's. Natlock, basically the remote
> studio's SPG was sync'd to TV Centre or Lime Grove by using remote control
> tones up a landline I think ?

Presumably every region's feed to the central studio had to have a
calibrated delay to compensate for the time taken for the Natlock signal to
reach the region and the region's output, synced to the Natlock *as it
receives it*, to return the central studio. I suppose as long as the same
circuit was always used, that would be a once-only setting, but as soon as
an alternative cable (or microwave link) was used instead, things would have
to be recalibrated. I would mean that every region was running with a
different delay to every other, such that all the signals reaching TV Centre
were in phase.

I'm inclined to say that a single country-wide SPG (Natlock) is better than
separate SPGs in each region which could differ in phase (and maybe even
frequency, though by a hopefully negligible amount). Either way, you need to
allow for cable delays, but with a central SPG, it's only a simple
sine/square wave that needs to be delayed, rather than a complete composite
video signal.

Nowadays, with digital framestores, I'm sure handling remote contributions
from regions of OBs of either analogue or digital TV is trivial, but it must
have been a real problem before framestores when you had to have some other
day of inserting the correct delay.

"Scott" <newsgroups@gefion.myzen.co.uk> wrote in message
news:tqorsgdlcelmnlfctbh20mqoghclk5mm3v@4ax.com...
> I am definitely missing something here. If each franchisee could
> insert its own adverts into a networked programme and return to the
> programme on time, why would there be a difficulty in moving from one
> company to another?

Region A contributes a programme to network. There is a finite delay (of
roughly 1 nanosecond per foot *) for the signal to reach the master
switching centre that distributes the signal to all the regions and hence to
each region's transmitters.

That programme ends and is followed by a programme contributed by Region B.
Region B's SPG may be out of phase with Region A's, and even if it's not,
there will almost certainly be a different delay because the signal is
coming from a different part of the country over a line of a different
length. The switching centre has to "persuade" the signals from Region A and
Region B to be in phase so a clean switch is possible. Insertion of adverts
within a programme is carried out at each region and the VT they use for the
adverts can be synced to the networked feed that they receive (the
contributing region must sync to this signal and not to their own SPG
because of the round-trip delay).

(*) An approximation based on the speed of light being about 3x 10^8 m/sec.
There is then the added complication that signals propagate at different
speeds (a proportion of the speed of light) through different cables.

On 30/12/2021 17:08, NY wrote:
>
> I'm inclined to say that a single country-wide SPG (Natlock) is better
> than separate SPGs in each region which could differ in phase (and
> maybe even frequency, though by a hopefully negligible amount). Either
> way, you need to allow for cable delays, but with a central SPG, it's
> only a simple sine/square wave that needs to be delayed, rather than a
> complete composite video signal.
It's for horses for courses. The BBC Natlock system would have been no
use at all for ITV, where you had 15 regional centres taking network
sources from up to 15 different locations.

It worked for the Beeb because London was the hub for most programmes.
ITV had no central hub

On 30/12/2021 17:19, NY wrote:
> "Scott" <newsgroups@gefion.myzen.co.uk> wrote in message
> news:tqorsgdlcelmnlfctbh20mqoghclk5mm3v@4ax.com...
>> I am definitely missing something here. If each franchisee could
>> insert its own adverts into a networked programme and return to the
>> programme on time, why would there be a difficulty in moving from one
>> company to another?
>
> Region A contributes a programme to network. There is a finite delay
> (of roughly 1 nanosecond per foot *) for the signal to reach the
> master switching centre that distributes the signal to all the regions
> and hence to each region's transmitters.
>
> That programme ends and is followed by a programme contributed by
> Region B. Region B's SPG may be out of phase with Region A's, and even
> if it's not, there will almost certainly be a different delay because
> the signal is coming from a different part of the country over a line
> of a different length. The switching centre has to "persuade" the
> signals from Region A and Region B to be in phase so a clean switch is
> possible. Insertion of adverts within a programme is carried out at
> each region and the VT they use for the adverts can be synced to the
> networked feed that they receive (the contributing region must sync to
> this signal and not to their own SPG because of the round-trip delay).
>
>
> (*) An approximation based on the speed of light being about 3x 10^8
> m/sec. There is then the added complication that signals propagate at
> different speeds (a proportion of the speed of light) through
> different cables.

You're completely overthinking the problem. All you need to ensure is
that the remote source is in phase with your own local SPG at the point
you switch to them. The distance the remote signal has travelled is
totally irrelevant

On Thu, 30 Dec 2021 16:57:10 -0000, "NY" <me@privacy.invalid> wrote:

>"JNugent" <jennings&co@fastmail.fm> wrote in message
>news:j365sfFbve8U1@mid.individual.net...
>> On 30/12/2021 11:28 am, NY wrote:
>>> I presume the master clocks for Thames and LWT would be at Euston and at
>>> Teddington respectively, so there isn't much distance between them for
>>> signal propagation delays.
>>
>> Euston and Teddington were both Thames establishments. LWT had the South
>> Bank studios and I think that for for a while, while waiting for
>> completion, the old Rediffusion studios at Wembley)
>
>Duh! Of course. I remember Magpie being advertised as coming from Teddington
>Lock - they may have given that as a correspondence address. And Magpie was
>weekdays not weekend.
>
>That means that The South Bank Show (with the nasally snuffling voice of
>Melvin Bragg) must have been a "weekend" programme if it was made by LWT
>(where "weekend" includes Friday night).

I'm sure it was shown in a weekend slot. Here is a nerdy question:
was there anything to stop LWT making a programme for the ITV network
that happened to be shown during the week (or indeed selling a
programme to Thames)?

On Thu, 30 Dec 2021 17:19:12 -0000, "NY" <me@privacy.invalid> wrote:

>"Scott" <newsgroups@gefion.myzen.co.uk> wrote in message
>news:tqorsgdlcelmnlfctbh20mqoghclk5mm3v@4ax.com...
>> I am definitely missing something here. If each franchisee could
>> insert its own adverts into a networked programme and return to the
>> programme on time, why would there be a difficulty in moving from one
>> company to another?
>
>Region A contributes a programme to network. There is a finite delay (of
>roughly 1 nanosecond per foot *) for the signal to reach the master
>switching centre that distributes the signal to all the regions and hence to
>each region's transmitters.
>
>That programme ends and is followed by a programme contributed by Region B.
>Region B's SPG may be out of phase with Region A's, and even if it's not,
>there will almost certainly be a different delay because the signal is
>coming from a different part of the country over a line of a different
>length. The switching centre has to "persuade" the signals from Region A and
>Region B to be in phase so a clean switch is possible. Insertion of adverts
>within a programme is carried out at each region and the VT they use for the
>adverts can be synced to the networked feed that they receive (the
>contributing region must sync to this signal and not to their own SPG
>because of the round-trip delay).
>
>(*) An approximation based on the speed of light being about 3x 10^8 m/sec.
>There is then the added complication that signals propagate at different
>speeds (a proportion of the speed of light) through different cables.

Sorry, but I'm still missing this, due to lack of technical knowledge.

If (say) Coronation Street could be sent to all the ITV companies
without any great difficulty that I can recall, and they could add
their own adverts, then why could the London service not be
transferred from Thames to LWT in the same way?

Could they not have timed an advertising break during the handover?

I'm not following this!

On 30/12/2021 04:57 pm, NY wrote:
> "JNugent" <jennings&co@fastmail.fm> wrote in message
> news:j365sfFbve8U1@mid.individual.net...
>> On 30/12/2021 11:28 am, NY wrote:
>>> I presume the master clocks for Thames and LWT would be at Euston and
>>> at Teddington respectively, so there isn't much distance between them
>>> for signal propagation delays.
>>
>> Euston and Teddington were both Thames establishments. LWT had the
>> South Bank studios and I think that for for a while, while waiting for
>> completion, the old Rediffusion studios at Wembley)
>
> Duh! Of course. I remember Magpie being advertised as coming from
> Teddington Lock - they may have given that as a correspondence address.
> And Magpie was weekdays not weekend.
>
> That means that The South Bank Show (with the nasally snuffling voice of
> Melvin Bragg) must have been a "weekend" programme if it was made by LWT
> (where "weekend" includes Friday night).

Like ABC in its day, LWT made programmes all week!

On 30/12/2021 05:37 pm, Scott wrote:
> On Thu, 30 Dec 2021 16:57:10 -0000, "NY" <me@privacy.invalid> wrote:
>
>> "JNugent" <jennings&co@fastmail.fm> wrote in message
>> news:j365sfFbve8U1@mid.individual.net...
>>> On 30/12/2021 11:28 am, NY wrote:
>>>> I presume the master clocks for Thames and LWT would be at Euston and at
>>>> Teddington respectively, so there isn't much distance between them for
>>>> signal propagation delays.
>>>
>>> Euston and Teddington were both Thames establishments. LWT had the South
>>> Bank studios and I think that for for a while, while waiting for
>>> completion, the old Rediffusion studios at Wembley)
>>
>> Duh! Of course. I remember Magpie being advertised as coming from Teddington
>> Lock - they may have given that as a correspondence address. And Magpie was
>> weekdays not weekend.
>>
>> That means that The South Bank Show (with the nasally snuffling voice of
>> Melvin Bragg) must have been a "weekend" programme if it was made by LWT
>> (where "weekend" includes Friday night).
>
> I'm sure it was shown in a weekend slot. Here is a nerdy question:
> was there anything to stop LWT making a programme for the ITV network
> that happened to be shown during the week (or indeed selling a
> programme to Thames)?

The South Bank Show was a Sunday staple.

LWT's earlier arts programme (1969/1970?) was "Aquarius", shown on
Friday evenings.

On 30/12/2021 17:44, Scott wrote:
> On Thu, 30 Dec 2021 17:19:12 -0000, "NY" <me@privacy.invalid> wrote:
>
>> "Scott" <newsgroups@gefion.myzen.co.uk> wrote in message
>> news:tqorsgdlcelmnlfctbh20mqoghclk5mm3v@4ax.com...
>>> I am definitely missing something here. If each franchisee could
>>> insert its own adverts into a networked programme and return to the
>>> programme on time, why would there be a difficulty in moving from one
>>> company to another?
>> Region A contributes a programme to network. There is a finite delay (of
>> roughly 1 nanosecond per foot *) for the signal to reach the master
>> switching centre that distributes the signal to all the regions and hence to
>> each region's transmitters.
>>
>> That programme ends and is followed by a programme contributed by Region B.
>> Region B's SPG may be out of phase with Region A's, and even if it's not,
>> there will almost certainly be a different delay because the signal is
>> coming from a different part of the country over a line of a different
>> length. The switching centre has to "persuade" the signals from Region A and
>> Region B to be in phase so a clean switch is possible. Insertion of adverts
>> within a programme is carried out at each region and the VT they use for the
>> adverts can be synced to the networked feed that they receive (the
>> contributing region must sync to this signal and not to their own SPG
>> because of the round-trip delay).
>>
>> (*) An approximation based on the speed of light being about 3x 10^8 m/sec.
>> There is then the added complication that signals propagate at different
>> speeds (a proportion of the speed of light) through different cables.
> Sorry, but I'm still missing this, due to lack of technical knowledge.
>
> If (say) Coronation Street could be sent to all the ITV companies
> without any great difficulty that I can recall, and they could add
> their own adverts, then why could the London service not be
> transferred from Thames to LWT in the same way?
>
Simply because the Thames/LWT switch was performed at BT (by an
automated  time switch) There was no means (staff or equipment) at the
BT Tower to sync the two sources into phase.
You can only perform that function at the physical location of the
switch, and it would have required BT to provide a bloke to monitor, and
'talk' his counterpart at LWT in.

Your local ITV company had a engineer comparing the phase of the
incoming network signal, with his own local sync pulses, and modify the
phase of the local pulses to ensure a clean cut. He was doing that just
before the start of each programme, and just before each ad break. So at
least every 20 mins or so. The phase would drift over that period, even
though each company in the network had 'precision' SPGs

In article <j365erFbvpvU1@mid.individual.net>,
Mark Carver <mark.carver@invalid.invalid> wrote:
> On 30/12/2021 16:05, NY wrote:
> > "Mark Carver" <mark.carver@invalid.invalid> wrote in message
> > news:j35rf0Fa39uU1@mid.individual.net...
> >> Up until the early 80s, your local ITV station would in the 10-15
> >> seconds or so before cutting to the network programme
> >> adjust the phase of the master SPG such that it drifted into sync
> >> with the network feed. Normally done by adding or subtracting one
> >> line per field.
> >> This had a drawback, that during this period any VTR or Telecine
> >> machine servos would go bananas because they were receiving no
> >> standard syncs.
> >>
> >> That's why the introduction into the programme was either a camera
> >> shot of the announcer, or a caption (such as a clock)
> >>
> >> When Frame Store Synchronisers appeared in the 80s, the ITV companies
> >> adopted those, so whatever was stuffed into the input of a Frame
> >> Store would be locked on its output to the local sync. That also
> >> liberated the companies to be able use VT derived logos etc into
> >> programmes.
> >
> > What technology did BBC use on programmes such as Nationwide when they
> > were switching network between feeds from various different regions
> > during the course of the programme? Everything had to be in sync at
> > the vision mixing centre (BBC TV Centre in Wood Lane or else Lime
> > Grove) irrespective of the fact that there would be a delay between
> > the contributing regional studio and the off air pictures that their
> > region's transmitters were broadcasting - equivalent to the round trip
> > regional studio-TV Centre-regional transmitter.

> The Beeb did the reverse technique to ITV's. Natlock, basically the
> remote studio's SPG was sync'd to TV Centre or Lime Grove by using
> remote control tones up a landline I think ?

Yes, that was Natlock. The steering information was, at a later date,
available in the frame blanking data period. Better for OB use, since an
extra sound line didn't ned to be booked (and paid for)

On the other hand, Sportsnight used fast Genlock on a separate sync pulse
chain. (6C - I installed it)

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On Thu, 30 Dec 2021 18:16:09 +0000, JNugent <jennings&co@fastmail.fm>
wrote:

>On 30/12/2021 04:57 pm, NY wrote:
>> "JNugent" <jennings&co@fastmail.fm> wrote in message
>> news:j365sfFbve8U1@mid.individual.net...
>>> On 30/12/2021 11:28 am, NY wrote:
>>>> I presume the master clocks for Thames and LWT would be at Euston and
>>>> at Teddington respectively, so there isn't much distance between them
>>>> for signal propagation delays.
>>>
>>> Euston and Teddington were both Thames establishments. LWT had the
>>> South Bank studios and I think that for for a while, while waiting for
>>> completion, the old Rediffusion studios at Wembley)
>>
>> Duh! Of course. I remember Magpie being advertised as coming from
>> Teddington Lock - they may have given that as a correspondence address.
>> And Magpie was weekdays not weekend.
>>
>> That means that The South Bank Show (with the nasally snuffling voice of
>> Melvin Bragg) must have been a "weekend" programme if it was made by LWT
>> (where "weekend" includes Friday night).
>
>Like ABC in its day, LWT made programmes all week!

You mean they were allowed to pre-record South Bank Show before 7 pm
on a Friday :-)

In article <sqkp4q$7qn$2@dont-email.me>, NY <me@privacy.invalid> wrote:
> "Mark Carver" <mark.carver@invalid.invalid> wrote in message
> news:j365erFbvpvU1@mid.individual.net...
> >> What technology did BBC use on programmes such as Nationwide when they
> >> were switching network between feeds from various different regions
> >> during the course of the programme? Everything had to be in sync at
> >> the vision mixing centre (BBC TV Centre in Wood Lane or else Lime
> >> Grove) irrespective of the fact that there would be a delay between
> >> the contributing regional studio and the off air pictures that their
> >> region's transmitters were broadcasting - equivalent to the round
> >> trip regional studio-TV Centre-regional transmitter.
> >
> > The Beeb did the reverse technique to ITV's. Natlock, basically the
> > remote studio's SPG was sync'd to TV Centre or Lime Grove by using
> > remote control tones up a landline I think ?

> Presumably every region's feed to the central studio had to have a
> calibrated delay to compensate for the time taken for the Natlock signal
> to reach the region and the region's output, synced to the Natlock *as
> it receives it*, to return the central studio. I suppose as long as the
> same circuit was always used, that would be a once-only setting, but as
> soon as an alternative cable (or microwave link) was used instead,
> things would have to be recalibrated. I would mean that every region was
> running with a different delay to every other, such that all the signals
> reaching TV Centre were in phase.

Each region "free ran". until it became controlled by Natlock.

> I'm inclined to say that a single country-wide SPG (Natlock) is better
> than separate SPGs in each region which could differ in phase (and maybe
> even frequency, though by a hopefully negligible amount). Either way,
> you need to allow for cable delays, but with a central SPG, it's only a
> simple sine/square wave that needs to be delayed, rather than a complete
> composite video signal.

Natlock wasn't a country-wide SPG. It was a way of syncing a remote SPC to
the one at TV Centre.

> Nowadays, with digital framestores, I'm sure handling remote
> contributions from regions of OBs of either analogue or digital TV is
> trivial, but it must have been a real problem before framestores when
> you had to have some other day of inserting the correct delay.

You didn't insert delay, you simply adjusted the remote SPG to come into
sysn.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

In article <5sursgdtdpmsfih3lku9iina60cueeju3j@4ax.com>, Scott
<newsgroups@gefion.myzen.co.uk> wrote:
> On Thu, 30 Dec 2021 18:16:09 +0000, JNugent <jennings&co@fastmail.fm>
> wrote:

> >On 30/12/2021 04:57 pm, NY wrote:
> >> "JNugent" <jennings&co@fastmail.fm> wrote in message
> >> news:j365sfFbve8U1@mid.individual.net...
> >>> On 30/12/2021 11:28 am, NY wrote:
> >>>> I presume the master clocks for Thames and LWT would be at Euston
> >>>> and at Teddington respectively, so there isn't much distance
> >>>> between them for signal propagation delays.
> >>>
> >>> Euston and Teddington were both Thames establishments. LWT had the
> >>> South Bank studios and I think that for for a while, while waiting
> >>> for completion, the old Rediffusion studios at Wembley)
> >>
> >> Duh! Of course. I remember Magpie being advertised as coming from
> >> Teddington Lock - they may have given that as a correspondence
> >> address. And Magpie was weekdays not weekend.
> >>
> >> That means that The South Bank Show (with the nasally snuffling voice
> >> of Melvin Bragg) must have been a "weekend" programme if it was made
> >> by LWT (where "weekend" includes Friday night).
> >
> >Like ABC in its day, LWT made programmes all week!

> You mean they were allowed to pre-record South Bank Show before 7 pm on a
> Friday :-)

It was only the broadcast times that were controlled - to even out the
advertising revenue.

Incidentally, TVC was often at it's busiest on a Sunday. It was the only
day that actors working in the theatre could make tv programmes.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

Scott <newsgroups@gefion.myzen.co.uk> wrote:
>
> You mean they were allowed to pre-record South Bank Show before 7 pm
> on a Friday :-)

Is that somehow different from recording it before 7pm?

--
Chris Green
·

On Thu, 30 Dec 2021 18:21:04 +0000, Mark Carver
<mark.carver@invalid.invalid> wrote:

>On 30/12/2021 17:44, Scott wrote:
>> On Thu, 30 Dec 2021 17:19:12 -0000, "NY" <me@privacy.invalid> wrote:
>>
>>> "Scott" <newsgroups@gefion.myzen.co.uk> wrote in message
>>> news:tqorsgdlcelmnlfctbh20mqoghclk5mm3v@4ax.com...
>>>> I am definitely missing something here. If each franchisee could
>>>> insert its own adverts into a networked programme and return to the
>>>> programme on time, why would there be a difficulty in moving from one
>>>> company to another?
>>> Region A contributes a programme to network. There is a finite delay (of
>>> roughly 1 nanosecond per foot *) for the signal to reach the master
>>> switching centre that distributes the signal to all the regions and hence to
>>> each region's transmitters.
>>>
>>> That programme ends and is followed by a programme contributed by Region B.
>>> Region B's SPG may be out of phase with Region A's, and even if it's not,
>>> there will almost certainly be a different delay because the signal is
>>> coming from a different part of the country over a line of a different
>>> length. The switching centre has to "persuade" the signals from Region A and
>>> Region B to be in phase so a clean switch is possible. Insertion of adverts
>>> within a programme is carried out at each region and the VT they use for the
>>> adverts can be synced to the networked feed that they receive (the
>>> contributing region must sync to this signal and not to their own SPG
>>> because of the round-trip delay).
>>>
>>> (*) An approximation based on the speed of light being about 3x 10^8 m/sec.
>>> There is then the added complication that signals propagate at different
>>> speeds (a proportion of the speed of light) through different cables.
>> Sorry, but I'm still missing this, due to lack of technical knowledge.
>>
>> If (say) Coronation Street could be sent to all the ITV companies
>> without any great difficulty that I can recall, and they could add
>> their own adverts, then why could the London service not be
>> transferred from Thames to LWT in the same way?
>>
>Simply because the Thames/LWT switch was performed at BT (by an
>automated  time switch) There was no means (staff or equipment) at the
>BT Tower to sync the two sources into phase.
>You can only perform that function at the physical location of the
>switch, and it would have required BT to provide a bloke to monitor, and
>'talk' his counterpart at LWT in.

I think I am getting it now. Why did the London companies uniquely
have to be routed via BT Tower? Was this because they provided the
sustaining service to all of ITV?

Why could they not have linked the LWT studio to the Thames studio and
the Thames studio to the BT Tower. This could have dispensed with BT
staff altogether and Thames could transfer control to LWT with staff
at both ends.

Or am I misunderstanding this completely?
>
>Your local ITV company had a engineer comparing the phase of the
>incoming network signal, with his own local sync pulses, and modify the
>phase of the local pulses to ensure a clean cut. He was doing that just
>before the start of each programme, and just before each ad break. So at
>least every 20 mins or so. The phase would drift over that period, even
>though each company in the network had 'precision' SPGs

I take it they couldn't give the job to Granada instead because this
would involve leasing 200 miles of telephone lines for the data..

On Thu, 30 Dec 2021 18:52:17 +0000, Chris Green <cl@isbd.net> wrote:

>Scott <newsgroups@gefion.myzen.co.uk> wrote:
>>
>> You mean they were allowed to pre-record South Bank Show before 7 pm
>> on a Friday :-)
>
>Is that somehow different from recording it before 7pm?

Note the smiley but what I meant was that Thames had the London
franchise until 7 pm Friday and LWT from then on. If the show were
recorded before 7 pm, LWT would not be a franchise holder.

In article <tp0ssgpisto5nrn26jsaql4gs8uij90tou@4ax.com>,
Scott <newsgroups@gefion.myzen.co.uk> wrote:
> On Thu, 30 Dec 2021 18:52:17 +0000, Chris Green <cl@isbd.net> wrote:

> >Scott <newsgroups@gefion.myzen.co.uk> wrote:
> >>
> >> You mean they were allowed to pre-record South Bank Show before 7 pm
> >> on a Friday :-)
> >
> >Is that somehow different from recording it before 7pm?

> Note the smiley but what I meant was that Thames had the London
> franchise until 7 pm Friday and LWT from then on. If the show were
> recorded before 7 pm, LWT would not be a franchise holder.

The Franchise was for broadcasting - not for making programmes. It would
have been different if they'd played Box and Cox in the same studios,

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

Scott <newsgroups@gefion.myzen.co.uk> wrote:
> On Thu, 30 Dec 2021 18:52:17 +0000, Chris Green <cl@isbd.net> wrote:
>
> >Scott <newsgroups@gefion.myzen.co.uk> wrote:
> >>
> >> You mean they were allowed to pre-record South Bank Show before 7 pm
> >> on a Friday :-)
> >
> >Is that somehow different from recording it before 7pm?
>
> Note the smiley but what I meant was that Thames had the London
> franchise until 7 pm Friday and LWT from then on. If the show were
> recorded before 7 pm, LWT would not be a franchise holder.

I was wondering how "pre-record" differs from "record", that's all. :-)

--
Chris Green
·

On Thu, 30 Dec 2021 19:28:06 +0000 (GMT), charles
<charles@candehope.me.uk> wrote:

>In article <tp0ssgpisto5nrn26jsaql4gs8uij90tou@4ax.com>,
> Scott <newsgroups@gefion.myzen.co.uk> wrote:
>> On Thu, 30 Dec 2021 18:52:17 +0000, Chris Green <cl@isbd.net> wrote:
>
>> >Scott <newsgroups@gefion.myzen.co.uk> wrote:
>> >>
>> >> You mean they were allowed to pre-record South Bank Show before 7 pm
>> >> on a Friday :-)
>> >
>> >Is that somehow different from recording it before 7pm?
>
>> Note the smiley but what I meant was that Thames had the London
>> franchise until 7 pm Friday and LWT from then on. If the show were
>> recorded before 7 pm, LWT would not be a franchise holder.
>
>The Franchise was for broadcasting - not for making programmes. It would
>have been different if they'd played Box and Cox in the same studios,

This was the reason for the smiley :-) Thames would have been allowed
to show programmes made by Rediffusion the week before.

On Thu, 30 Dec 2021 19:24:07 +0000, Chris Green <cl@isbd.net> wrote:

>Scott <newsgroups@gefion.myzen.co.uk> wrote:
>> On Thu, 30 Dec 2021 18:52:17 +0000, Chris Green <cl@isbd.net> wrote:
>>
>> >Scott <newsgroups@gefion.myzen.co.uk> wrote:
>> >>
>> >> You mean they were allowed to pre-record South Bank Show before 7 pm
>> >> on a Friday :-)
>> >
>> >Is that somehow different from recording it before 7pm?
>>
>> Note the smiley but what I meant was that Thames had the London
>> franchise until 7 pm Friday and LWT from then on. If the show were
>> recorded before 7 pm, LWT would not be a franchise holder.
>
>I was wondering how "pre-record" differs from "record", that's all. :-)

I probably wanted to emphasise I meant recording the programme before
transmission (when LWT did not hold the franchise) rather than during
transmission (when it did). I think my attempt at humour has fallen
flat.