Alresford UAX12
The first automatic exchange on the railway was installed at Alresford and comprised of a UAX12 A rack and C rack giving a maximum capacity of 25 lines.
All equipment was pre 2000 type and the numbers were in the range 2XX.
A complete UAX12 had been purchased from Hursley, near Winchester when it was withdrawn from service with the introduction of STD in the early 1970s.
8 racks of UAX12 equipment were obtained for the sum of £10, somewhat of a bargain, comprising of 3 A, 3 B and 2 C racks, this equipment was new in 1944.
The A rack contained 4 selectors ( believe they were called link circuits ) 25 line circuits, 4 x 50 point uni-selector line finders plus 4 junction relay sets and the C unit the main distribution unit ( MDF ) common services, tone and ringer relay sets.
The B rack was associated with an A rack, had 20 line circuits, 2 selectors and 2 junction relay sets but these racks were not used at the railway.
The selector would discriminate on the first digit dialled, in the case of the Alresford exchange the digit 2 would cause the selector to restore to normal and then act as a final selector for the last two digits. An initial digit of 9 caused the selector to act as a group selector and search for a free junction relay set.
There was a multi-metering relay set associated with each junction relay set, this was strapped to give call barring depending on what was dialled.
The UAX12 at Hursley was a double unit with numbers in the range 2XX and 5XX, if a subscriber on the 2XX unit called one on the 5XX unit the selector would step to level 5 and act as a group selector to find a free selector in the other unit which then acted as a final selector. The selectors were modified to allow this, there were at least 3 variants of these selectors that I know of.
From memory the first unit, 2XX numbers, comprised 2 A, 2 B and 2 C racks and the second unit, 5XX numbers 1 A and 1 B rack.
If there were 6 circuits from the first to the second unit this meant that the directory numbers 251 to 256 couldn't be allocated to customers and if there were the same number of circuits in the opposite direction 521 to 526 couldn't. Junctions to the parent exchange were on level 9, this ruled out customer numbers 291 - 298 and 591 - 8 if 8 junctions were provided on each unit.
The linefinders homed after each call and incoming junctions were allocated to the early outlets.
As the exchanges were used in unheated building the racks had large removable panels at the front and rear.
Its replacement was a UAX13S, this was a standard UAX13 fitted with discriminators for linked number scheme working. The numbers became 752XX and 755XX. The local code from Winchester was 75.
Additional selectors for use as spares came from another recovered UAX12 at Cholderton in Wiltshire.
Some years later when the UAX13S was replaced with a System X exchange a number of discriminators were obtained for a scheme on the railway that was never implemented, they remain in store, unused, to this day.
The numbers changed to 7752XX and 7755XX with the introduction of the digital exchange, further numbers were later provided in the range 7753XX and 7754XX.
With the expansion of the line thoughts were of getting more modern equipment, one line of enquiry was with Lloyds Bank in London who had an internal phone network using PAXs that was being modernised, we were offered an exchange but nothing ever became of it. I seem to recall the equipment, type forgotten and never seen, used some form of discriminator circuit.
For reasons unknown a quantity of Director equipment was obtained but never used.
In case nothing newer was available plans were made to adapt the existing exchanges. Recently details were found of outline plans to build a tandem exchange at Ropley and modify the UAX12s, these notes have been added at the end of the
linked number scheme section. Possibly the third A unit would have been used at Alton but some form of MDF and common services would have had to be built.
Option C would have been used, a brief detail of operation - assume one is dialling Ropley 321 from Alresford, an outgoing call would be made in the normal manner using a junction dialling code, 9 in this case. This would connect to a 2000 type selector in the tandem exchange, the next digit, 3, steps the tandem selector which selects a free junction to the Ropley UAX12 exchange, there would be an incoming relay set added in the UAX12. When this set was seized a uniselector would find and connect to a free selector, which would act as a final selector when the last two digit, 21, are dialled.
The diagrams have been lost over the years but a trial relay set had been made to be used to terminated incoming junctions in the UAXs.
Type 4 uni-selectors, which were difficult to obtain in those days, were to be used. A number had been found in a junk shop in Maidstone.
We were very fortunate to be offered a complete Standard Telephone and Cables PABX that was being replaced by Plessey in Northampton; this had a capacity of 150 extensions in the range 200 - 349 using around 60 4000 type selectors.
Parts of the Plessey exchange replaced the UAX12 at Alresford in October 1981, 2 racks were provided giving a maximum of 50 extensions, the numbers changing to 22XX, the first stage of a planned
linked numbering scheme.
Rack at Plessey - selector E2 appears to have a fault, plus it appears this shelf has a split multiple. 4000 type selectors.
Incoming calls from the public network were answered on one of two operator consoles, each exchange line relay set had a dedicated 1st selector and calls were extended via this selector to an incoming final selector. This differed from an ordinary final selector used on extension to extension calls in that the transmission bridge was located in the exchange line relay set.
Plessey Northampton - removal of exchange.
The UAX12 exchange went to the Dart Valley Railway along with the 3 B racks, if it was ever used again is not known, but I was informed some years ago parts had surfaced on the Welsh Highland Railway at Portmadoc.
I cannot remember what happened to the third A unit, it could have also gone West.
Above is a directory for the exchange, the Alresford numbers were in the range 221X and 220X.
The exchange room was a little decrepit so later the equipment was physically moved sideways, the room partitioned and the vacated area renovated, into this area another exchange was installed in 1985.
from Turntable October 6th 1984
Two redundant AC9 racks from the main Post Office exchange in Winchester, which we had to cut down from 10ft 6 ins, were used to mount selector and relay set shelves from the Plessey exchange.
One rack was used for the line finders and selectors and the other for relay sets.
A ringer rack from the BBC TV Centre with 2 type 45 ringers completed the installation. At the time of collection a PABX with 8000 extensions was being scrapped.
Again 50 extensions were provided, 4000 type selectors were used initially but were later replaced with 2000 type a type I was more familiar with.
100 outlet 10 position bank multiples were used, one shelf of 1st selectors, another for second and in-coming selectors and a third for final selectors. Four level 0 and 1 relay sets from UAXs were used as the junction relay sets to Ropley accessing four bothway junctions via junction hunters.
The extensions and junctions were transferred from the old to the new exchange and the old equipment scrapped, it was not reused at Alton as mentioned above. A Power Plant 223 with end cell switching was used until replaced by a PP2040 some years later.
The numbers were now in the range 222X to 225X.
The Mogul 9th May 1985
A number of selectors and relay sets were obtained from the CEGB at Guildford when they replaced their Strowger PABX4 exchange and provided a useful supply of spare equipment.
From the top
Miscellaneous relays
Final selectors - 5 for ordinary calls, 4 for i/c call transfer and 1 for TKO
5 second selectors, 4 incoming junctions from Ropley
Miscellaneous relay sets
10 1st selectors
10 line finders
50 line circuits
MDF at the rear, all soldered connections.
A fourth rack, from Itchen Abbas UAX13, was added later for assorted relay sets, a planned 1 plus 4 carrier system and a shelf for a TRT284 call sender.
It was fitted next to the rack shown above.
Later the full width relay set rack was replaced by a narrower one with 5 shelf positions, by that time a lot of the existing relay sets were no longer being used and the extra floor space created was used to instal a 62 type carrier rack, another carrier project that came to nothing.
At this time the Ropley junctions were changed to 2 direct circuits for Ropley traffic and 2 for tandem calls, if both the direct circuits were busy Ropley calls could overflow onto the tandem circuits.
2-10 PBX final selectors were used here and at Ropley.
When withdrawn from service this exchange went to East Sussex for further use.
Selector rack on the right and the ex BBC ringer rack on the left.
Two sets of gas combination standby batteries were housed externally in 2 glass fibre cabinets, these had replaced one set of lead acid cells located in the building, later a Power Plant 2040 was installed.
Disposal of the ex BBC ringer rack 2004 Phil Mousley (OIC IT) on the left.
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