ITV regions debate

[telebox2001]

So in that instance, Glasgow would still establish a connection to Manchester at 7pm but rather than put the feed to air, they would make a recording and play that tape out on STV at the time they wanted.

It all worked very much like late edit/turnaround programmes are still done today.

Do STV still record programmes off the line from Chiswick, or is this more sophisticated now? In the case of shows like football highlights which might start 20 minutes later, do they effectively just show a delayed version of the feed from Chiswick (effectively a pro-grade PVR operation?)

[Markymark]

So in that instance, Glasgow would still establish a connection to Manchester at 7pm but rather than put the feed to air, they would make a recording and play that tape out on STV at the time they wanted. 

It all worked very much like late edit/turnaround programmes are still done today.

Do STV still record programmes off the line from Chiswick, or is this more sophisticated now?  In the case of shows like football highlights which might start 20 minutes later, do they effectively just show a delayed version of the feed from Chiswick (effectively a pro-grade PVR operation?)

Centralised playout from Chiswick is a relatively recent thing,  and centralised playout from LNN South Bank started to happen around the turn of the century. Before that everything was VTR based, and before 1993 any programme was played out to the rest of the network via BT circuits, usually from its originating company. So for instance BT configued the ITV distribution network so that Granada played out Corrie at 19:30 to network. For stuff that had different showing times around the UK (Crossroads is a good example) then some ITV companies would form a mini network to do that. I think Southern recorded Crossroads from ATV, then played it out at 17:20 locally, and also to HTV and STV

Timeshifting a live programme that was still in progress using VTRs was a hairy business. I think BBC Cardiff did it weekly with something. Involved three  VTRs and immense concentration!

[Brekkie]

So in that instance, Glasgow would still establish a connection to Manchester at 7pm but rather than put the feed to air, they would make a recording and play that tape out on STV at the time they wanted.  

I always regret asking the technical questions when I get the technical answer but how exactly did the regions play out content to each other, especially pre-satellite?

[Steve in Pudsey]

Each region head multiple BT Local Ends, so they could potentially have an incoming programme from Central on the air while they recorded one from Thames.

I think at the Blue place Tony Currie mentioned that STV had more incoming circuits than Grampian so on certain occasions where the two stations were sharing a programme it was convenient to have Grampian play it out so as not to tie up their inbound circuit.

[Brekkie]

So delivered over a phone line then long before that was a way many of us consumed our television?

[Neil Jones]

So delivered over a phone line then long before that was a way many of consumers our television?

Fibre optic IIRC, discussed a few times over on the blue place.
Think they all went via microwave initially which was later replaced by fibre as it was (it says here) microwave was more resilient to nuclear attack.

Don't think it was a "phone line" as we know it today, probably closer to a Virgin style setup?

[Inspector Sands]

So delivered over a phone line then long before that was a way many of consumers our television?

Fibre optic IIRC, discussed a few times over on the blue place.
Think they all went via microwave initially which was later replaced by fibre as it was (it says here) microwave was more resilient to nuclear attack.

Yes BT or the Post Office had a big microwave network crossing the country, but of course the connectivity to individual stations will have been cable from telephone exchanges. In the 80's fibre optic cables arrived and gradually replaced the microwave network.  

http://dgsys.co.uk/btmicrowave/  is a great site giving details about the network listing all the sites in it but it looks like it's being rebuilt and there's a lot missing. The map and index of sites is still online here: http://dgsys.co.uk/btmicrowave/sites/mapall.php

The site has a lot of information about ITV connectivity, for example this page is all about the BT network down to Plymouth built for the start of Westward TV: 
http://www.dgsys.co.uk/btmicrowave/routes/109.php

and the connectivity between Bristol and Cardiff for HTV: http://www.dgsys.co.uk/btmicrowave/routes/186.php

and TVam in Knutsford http://dgsys.co.uk/btmicrowave/sites/293.php

BT's backbone network or microwave links was built to be resilient to things like nuclear attack and was said to have civil defense functions as well as telephone and television and radio traffic. Hence it was kept very secretive despite the massive concrete towers that everyone knows about such as the PO Towers in London and Birmingham. 
https://www.subbrit.org.uk/features/back...y-network/
 

Don't think it was a "phone line" as we know it today, probably closer to a Virgin style setup?

I'm not sure what you mean by a 'Virgin style setup', but no the connectivity wasn't using phone lines. They were carried on the same network though, they used to quote connections as being able to carry x number of phone calls or 1 TV channel. Until the 80's I think they were the only providers allowed to carry TV in the same was they were the monopoly phone provider

[telebox2001]

ISTR that when BT was first privatised, it was forbidden from establishing a cable television network. Not that I'm sure it would have even been possible to do that on the 80's network!

[Steve in Pudsey]

I think BT had first refusal on providing permanent circuits but if they declined (for reasons of practicality or cost) the BBC and IBA could self provide a microwave link, with certain caveats.

Many of the more remote parts of the transmitter network involved an intermediate site receiving off air signals and rebroadcasting them on a microwave circuit to another transmitter.

[Markymark]

The self provision of circuits by the BBC and IBA was governed essentially by whether BT/GPO could be bothered or not to provide the circuit themselves.

In the 60s some transmitters were fed by the broadcasters' own links for vision, but the audio via GPO landline.

An audio landline was physically nothing more than a twisted pair of cables, no different to a phone line, and usually sharing a multicore bundle of phonelines in street ducts. Sometimes they'd end up getting accidentally connected to someone's phone line. There was the case in the 70s of some bloke in Bristol getting connected to Radio Bristol's transmitter one afternoon! They jumped from telephone exchange to telephone exchange as part of that journey

A video landline was referred to as a tube,  basically a coax cable rather like a domestic aerial cable, but robustly wrapped up in a protective sheath, and run in ducts under the street.

A microwave intercity vision link could carry one TV vision circuit, or 960 phone circuits. The broadcasters were charged the equivalent of 960 phone calls. The
phone services took priority in any failure condition

In the 70s the BBC adopted digital sound in syncs on their distribution and contribution vision circuits. The GPO contracts usually tied a landline for audio,  so it didn't save money, but the BBC redeployed the audio lines for radio distribution, and PABX (internal phone service) That's probably why the IBA/ITV carried on with audio landlines until 1988 when NICAM came along. C4 used sound in sync from the outset

That said Thames used sound in sync on their circuits between Euston and Teddington. Probably,  like the Beeb they redeployed the associated audio lines internally.

[telebox2001]

Am I right in saying that before digital multiplexing came along an analogue landline was capable of carrying broadcast quality audio with a ceiling of somewhere like 12KHz? It was merely the equipment at either end that reduced the sound quality.

Now of course it's multiplexed using low/high pass filters to fit more "calls" onto a single line, but in the olden days that's how I understood it to be.

[technologist]

It depended ….. some problems ..
did it have loading coils on it … if you increase the inductance if the line you get less loss at higher frequencies
so a 3.4 KHz audio signal goes further
How much cross talk - that gets worse at higher frequencies
Did it have ringers on it .. so times there was a ring amplifier some where along it ..

And as I have indicated a twisted pair gets more lossy with frequency,
so how much equalisation could be a problem… particularly if it was made up of different types of cable .

Digits over twisted Pairs / 4 wires came in about 50 years ago with 30 channel PCM /E1
But until S screen cables came in you either had to use alternate pairs so halving capacity
Or two,cables to prevent cross talk.

Audio over good twisted pair/4Wire was 12 telephone channels on carrier.
The BBC World service had a bay Which had 6 circuits if say 6Khz
to feed each of the 4 main transmitter sites .

[Robertclark125]

I think at the Blue place Tony Currie mentioned that STV had more incoming circuits than Grampian so on certain occasions where the two stations were sharing a programme it was convenient to have Grampian play it out so as not to tie up their inbound circuit.

Would this explain what I'm about to describe, from the days of ITV Schools on 4, 1987-1993. There were a couple of times a week, where Scotland saw a different programme from everyone else on C4 at the time. Where I live, in the STV area, as the rotomotion device came on for the next programme, albeit without the programme information, where was an on screen glitch, before we saw the rotomotion device but with the opt out programme details.

My guess would then be, Grampian played it out as opposed to STV, and that in the Grampian region on C4, there wouldn't have been a glitch. Grampian would've simply inserted their own rotomotion device over the network one, like they would with adverts.

[Markymark]

Am I right in saying that before digital multiplexing came along an analogue landline was capable of carrying broadcast quality audio with a ceiling of somewhere like 12KHz?  It was merely the equipment at either end that reduced the sound quality.

A passive twisted pair phone line has a bandwidth way way beyond the audible audio range, it's the whole essence of ASDL and VSDL broadband, you have to rely on responses up into MHz, and indeed on short runs you can stuff analogue video down them (The BBC did that in the 50s and 60s in parts of London). What limits the bandwidth and quality is the active equipment and loading/matching at each end of the line and also capacitance and inductance of that cable, which in turn results in Group Delay' effects. Put simply, different frequencies travel at different velocities along the line, which results in nasty distortion at distance.

Today the only analogue path left is between your house and the exchange. Between exchanges it's all digital now, and of course with FTTP being rolled out, the copper analogue route is fast vanishing for everyone

[i.h]

ISTR that when BT was first privatised, it was forbidden from establishing a cable television network.  Not that I'm sure it would have even been possible to do that on the 80's network!

The big thing was coax, in earlier networks this was coax all the way from the headend but BT were also looking at an early form of what is now called "hybrid fibre coaxial", with two way communications, even video on demand via laserdisc jukeboxes. Other countries' telcos were not banned from doing so (eg Germany) and perhaps that explains why cable TV is more widespread than it is here.

IIRC some of these networks remained in BT ownership (though as a standard one-way cable TV system) though operations were shifted to NTL and then Virgin

The ban was on offering services to end users, not to businesses like the broadcast industry (where of course the Post Office and later BT were a monopoly until other telcos like Mercury or Energis came along)

https://www.youtube.com/watch?v=-1AiM1S8MGk

Fibre was already moving forward within the network and of course BT wanted to run fibre to the home by the end of the decade. By the end of the 90s BT had fully digital telephone switching and transmission, as Mark says it was then only the last bit to the home that remained analogue (though it didn't have to be, that's what ISDN was for, which achieved limited success for residential users who wanted two phone lines or faster internet speeds than dialup gave them). In the broadcast sense ISDN was a lot more popular as it enabled high quality audio transmission without any real effort or fuss, especially for radio.

I should however be pedantic and point out that digital phone lines are back again, even without FTTP, as ISPs move towards VoIP delivered over any form of internet connection, copper, fibre, mobile