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[WWWombat]

While looking up something recently, I stumbled on this document:

A Short History of Telecommunications Transmission in the UK

With a transmission focus, this is all about "backhaul" - the trunk networks that criss-cross the UK, connecting exchanges.

Interesting...

[licquorice]

Happy memories for me as a core transmission man from FDM days through to DWDM. Keith Ward was actually my ultimate boss at one point.

[Black Sheep]

Happy days, Licq ....... when decision-makers actually knew the job. 

[licquorice]

Indeed, we were all engineers back then, not bean counters.

[licquorice]

Interesting reading about the 'phantom' circuits derived from the centre taps of transformers, they were actually used to transmit the music circuits he goes on to discuss. There were also 'double phantom' or 'ghost' circuits that were derived from the centre taps of phantom circuits!!! Talk about trying to get a quart into a pint pot, although, as would be expected, the double phantom circuits were quite unstable and were used for alarm circuits etc.

[licquorice]

The cables carrying the 24 channel Carrier System No7 that he refers to were converted to carry early PDH 8Mb/s digital signals, a Plessey system known as EDL8 which had to have buried regenerators at 3Km intervals. These were a nightmare to commission, the cables were from the thirties and because of severe crosstalk problems only about half of the pairs could be used and was a process of trial and error juggling which pairs to use between each repeater to achieve the best results.

Must stop reminiscing!!

[Black Sheep]

No, please don't. I find it incredibly interesting reading about it ....... far more technical back then.

[tickmike]

On 'Figure 2 An H-pole' I remember them  , Are single core wires on poles used or about today or has all that gone ?.

[licquorice]

Another interesting snippet about the carrier cables is that pairs 1&2 never appeared above ground and were used for defence circuits. When the rest of the cable popped up into a repeater station, pairs 1&2 used buried amplifiers (by buried, I mean a pressurised steel case sitting in the bottom of a manhole). When the cables were converted to EDL8, pairs 1&2 remained below ground and were used to connect the EMSS (Emergency Manual Switchboard System) used for civil defence in the cold war. Because 120 phone circuits was a lot of capacity to lose just to dedicate the use for the EMSS, there were 2 terminal installations of the EDL8 kit, one in the basement of exchanges and one in the normal repeater station. Normal operation was for the system to be switched to the terminal upstairs via the basement terminal, but if necessary the upstairs terminal could be disconnected.

[licquorice]

On 'Figure 2 An H-pole' I remember them  , Are single core wires on poles used or about today or has all that gone ?.

I can't imagine there are any open copper wires left now. I certainly remember working on them though, not much fun climbing a pole through a nest of wires on a cold wet day with ringing current catching your ears!!! Even then crosstalk was a problem on the H-Pole trunk routes and transposition poles were placed at regular intervals to change the postion of the pairs within the nest to reduce crosstalk.

[Black Sheep]

Another interesting snippet about the carrier cables is that pairs 1&2 never appeared above ground and were used for defence circuits. When the rest of the cable popped up into a repeater station, pairs 1&2 used buried amplifiers (by buried, I mean a pressurised steel case sitting in the bottom of a manhole). When the cables were converted to EDL8, pairs 1&2 remained below ground and were used to connect the EMSS (Emergency Manual Switchboard System) used for civil defence in the cold war. Because 120 phone circuits was a lot of capacity to lose just to dedicate the use for the EMSS, there were 2 terminal installations of the EDL8 kit, one in the basement of exchanges and one in the normal repeater station. Normal operation was for the system to be switched to the terminal upstairs via the basement terminal, but if necessary the upstairs terminal could be disconnected.

The EMSS ?? Were they akin to, or linked with the (From memory) the WB early warning systems ?? I always wondered if the Exchange TO was having a laugh at we noobies expense when he said these systems existed. I've certainly seen signage in the past with (Again from memory), WB800, WB1200 written ........ cannot remember where though as it didn't involve me at the time, so didn't really enquire further.

[Black Sheep]

On 'Figure 2 An H-pole' I remember them  , Are single core wires on poles used or about today or has all that gone ?.

I can't imagine there are any open copper wires left now. I certainly remember working on them though, not much fun climbing a pole through a nest of wires on a cold wet day with ringing current catching your ears!!! Even then crosstalk was a problem on the H-Pole trunk routes and transposition poles were placed at regular intervals to change the postion of the pairs within the nest to reduce crosstalk.

I bet it's 10yrs since I last saw 'Open wires', even then it was classed as a 'novelty' to still see them. The only scenario's I can imagine they still exist is out in the wilds of Scotland, or the hills of Wales ...... ??

[Weaver]

@licquorice -looking at pictures of the old H poles. The wind load on them must have been bad? I can't imagine they would survive too well here in Skye.

[licquorice]

They were all part of the civil defence system.  WB400/WB1400 was yet another system I worked on, converting all the local UAX's from WB400 to WB1400 (which was scrapped soon after). The WB400/1400 system was the '4 minute warning' broadcast sytem that was sent to receivers located at post offices, police stations, civil defence personnel's houses etc. It utilised the speaking clock distribution network to operate. There's quite a good description here http://www.ringbell.co.uk/ukwmo/Page212.htm

[Black Sheep]

Wow !! Thanks for that ......... I've searched our infernal systems, but no sign of the WB's anywhere. As I say, I couldn't tell for certain if the TOA was pulling my leg or not, especially when he also mentioned about underground bunkers in the middle of fields etc (Not the large ones, like the immense one below Manchester's streets).

I did see a programme once (Not sure if it was the 'One Show'?), that saw a presenter actually locate one of these rural bunkers and go down it.

So, with that and your input ...... may my old TOA rest in peace ...... he wasn't taking the .....