> it was stated that a passive optical network would be much
> more reliable and use far less power. Apparently they have a huge
> electricity bill powering all those cabinets. Another interesting
> factoid is they have 300,000 cabinets.

The optical cabinets should use zero power, unless they have a layer 3 switch
or fibre repeater, and those are usually in buildings.

One reason for the high power use is the pairs of tall VM cabinets you see on
main road contain telephone exchange line concentrator kit, lots of 30 year old
electronics racks, and the copper coax line drivers, that is what allowed VM to
have one main 'exchange' per town serving properties 50 miles away, common in
the USA due to the distances. BT System X could have used remote concentrators
but BT rarely did so since they had exchange buildings everywhere, just the odd
remote business park and estate.

But the smaller VM cabinets are just passive distribution for coax and copper
pairs.

Angus

On Friday, 28 April 2023 at 19:02:40 UTC+1, Angus Robertson - Magenta Systems Ltd wrote:
> > it was stated that a passive optical network would be much
> > more reliable and use far less power. Apparently they have a huge
> > electricity bill powering all those cabinets. Another interesting
> > factoid is they have 300,000 cabinets.
> The optical cabinets should use zero power, unless they have a layer 3 switch
> or fibre repeater, and those are usually in buildings.
>
> One reason for the high power use is the pairs of tall VM cabinets you see on
> main road contain telephone exchange line concentrator kit, lots of 30 year old
> electronics racks, and the copper coax line drivers, that is what allowed VM to
> have one main 'exchange' per town serving properties 50 miles away, common in
> the USA due to the distances.

And that the losses on coax are high, so you have to drive with significant power if the run is of any length. Even for satellite grade CT100
https://www.farnell.com/datasheets/1927177.pdf
the losses at just 100MHz is 6.5dB/100m.

> BT System X could have used remote concentrators
> but BT rarely did so since they had exchange buildings everywhere, just the odd
> remote business park and estate.

System X replaced old "whir and bang" (mainly Strowger) electro-mechanical exchanges from about 1980 onwards. The wiring to the exchanges was infrastructure dating back up to a century - so no need for concentrators, although BT would install concentrators on new build and to replace expired 'village' exchanges.

>
> But the smaller VM cabinets are just passive distribution for coax and copper
> pairs.
>
> Angus