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[Black Sheep]

I can't see the details on the equipment to the right of the battery-set ….. but I'm guessing it's a rectifier unit ?? From my very poor memory, the ones I used to work on were Rec 231's and 233's ….. but we didn't have any small UAX's on our patch, so they were bigger than this unit here.

[licquorice]

Yes, that was the rectifier, can't remember any details though. The WB400 (cold war early warning system) kit had its own dry cells in the bottom of its cabinet.

[4candles]

Just a little observation/clarification.

The UAX13 is sometimes mistakenly referred to as an 'Unmanned Automatic Exchange'. While it's true that they were unmanned - as were SAXs (Small Automatic Exchanges), Mr Cat is correct in using the term 'Unit Automatic Exchange'.

The name derives from the fact that linefinders, group selectors, final selectors and subscribers' meters for 50 lines were accommodated on a single rack. An early modular system one might say. Need 50 more lines? Add another rack.

[burakkucat]

My thanks to B*Sheep, licquorice and 4c for their contributions. It is always helpful to hear details from those who, in their time, were a lot "closer" to the actual equipment being discussed. 

[Weaver]

@BlackSheep  et al

thank you for your generosity, a superb answer which draws a picture.

Basic stuff such as this isn't easily come by. I seem to remember that Kitz got a guided tour courtesy of BT. That's what I need, few of us have such an opportunity.

[Fuggi]

From the exchange photo the equipment looks like a power plant 227 and cells secondary 22/200 eg 200 ampere/hr.

[WWWombat]

Hehe. Really interesting to see some of the real kit in use - I'm too used to seeing everything in a lab environment.

Anyone seen this site on UAX's:
http://www.uax.me.uk/
?

[licquorice]

Hehe. Really interesting to see some of the real kit in use - I'm too used to seeing everything in a lab environment.

Anyone seen this site on UAX's:
http://www.uax.me.uk/
?

Yes, interesting site. Spent a lot of time adding extra A Units to UAX13s in the seventies. We also had a couple of UAX12s and the larger UAX14s.

[Black Sheep]

Just a little observation/clarification.

The UAX13 is sometimes mistakenly referred to as an 'Unmanned Automatic Exchange'. While it's true that they were unmanned - as were SAXs (Small Automatic Exchanges), Mr Cat is correct in using the term 'Unit Automatic Exchange'.

The name derives from the fact that linefinders, group selectors, final selectors and subscribers' meters for 50 lines were accommodated on a single rack. An early modular system one might say. Need 50 more lines? Add another rack.

I never knew that, regarding the true meaning of the UAX acronym. I've just done a quick search on our internal systems  for 'UAX' and the first 'Hit' highlights a particular estates issue at 'xxxxxxxxx Unmanned Automated Exchange'. 

I absolutely understand the full and proper term, and thank you for explaining why it is properly referred to as 'Unit ......'. 

[licquorice]

With being a modular construction, it meant that although 50 subscribers could be accomodated within one A unit, only 8 of them could make calls concurrently as there were only 8 Linefinders on an A unit.

[Black Sheep]

With being a modular construction, it meant that although 50 subscribers could be accomodated within one A unit, only 8 of them could make calls concurrently as there were only 8 Linefinders on an A unit.

Thanks for the further info, Licq ........ 

Although a marvel of modern technology in it's day, your explanation of its limitations shows just how far we've gone in just under 30yrs !!
Who'd have thunk it 

[licquorice]

In my relatively brief 40 years on the job there was one exchange that I converted from a manual switchboard above the Post Office to a Strowger, from a Strowger to a Crossbar and saw the Crossbar replaced by a digital concentrator!! Definitely come a long way.

[Weaver]

@licquorice -much respect.
That's how I feel when I think about the DEC VAX 11/750 that a dozen of us used to share back in 1983: 30A mains, its own room and the brute was the size of a couple of fridges, took three guys to lift it, 0.65 MIPs for a mere £150k. That compared with my wife's mobile phone : >6000 times faster (not sure, lost count some time ago) around 1000 times the RAM. The 64-bit ARM-based iPad I'm writing this on - even more frightening!

[WWWombat]

With being a modular construction, it meant that although 50 subscribers could be accomodated within one A unit, only 8 of them could make calls concurrently as there were only 8 Linefinders on an A unit.

So the line finders stayed in the speech path for the duration of the call? That surprised me, but perhaps it is a cost of making easy-to-add modular units.

It wouldn't have been popular in the days of dial-up!

[licquorice]

Yes, the 8 Linefinders were hard wired to  8 of the 10 Group Selectors, which all remained in the speech path throughout. The other 2 Group Selectors (if fitted) were used for Incoming Junction (Trunk) ccts from the parent exchange.