Photos of Phones and Phonographs (occasionally)
Connecting my PAX collection
My collection of phone exchanges hasn’t really grown at all in over a year now, but they’re still all very much isolated islands. You can’t phone from one exchange into any of the others (with the exception of the 50 line exchange and the asterisk server, which are connected by a tie line which you access by dialling 50) – I’d like to link them all up, in a manner similar to that shown above.
Extensions on the asterisk server are 2 digits (because it makes the dialplan consistent) To get from PAX extension 26 to VOIP extension 81, you dial 5081. The 50 connects you to asterisk, and 81 connects you to the VOIP phone. The asterisk server has been set up so that you also dial 50 to access the PAX, so from 81 you can dial 5026 to call in the other direction.
This gives a nice consistent 4 digit dialing scheme! Great!
My 10 line PAXs throw a bit of a spanner into that though as they have a single digit numbering scheme. I can have extra outgoing tie lines from the 50 line PAX (for example on 30) but if I were to connect them directly, they’d be 3 digits and that would *never* do!
So at the weekend, I designed and built this relay set. It hangs off the 30 tie line, and stores the next digit you dial. Depending on what digit you dial, it can connect you to one of up to ten 10 line exchanges (I don’t have 10, but it’s best to plan ahead!) So now, Dialing 30 connects you to this relay set, dialing 0 connects you to a 10 line PAX, and then you can ring the phone at extension 4 – giving you 3004! Yay! 4 digit phone numbers!
OK, so going the other way isn’t quite as neat (Dial 0 to get out of the 10 line PAX, then you’re landed straight into the 50 line, so dialling 026 will ring extension 26, or 05081 will dial VOIP 81) but it’s better than nothing… and my ATE 10 line PAX doesn’t have any outgoing tie lines at all yet so I’m not that worried!
Anyway, I’m quite pleased with this project as it’s the first non-trivial relay set I’ve designed, built, and debugged without assistance! I say designed, most of the circuit elements are pretty standard. The junction half of the circuit is based on the auto-auto junctions we use at the railway. It’s a pretty basic stone transmission bridge, with 2 stage dropback and the A2 contact repeating dial pulses out to the line.
The uniselector which reacts to the dialed digit is controlled by a circuit based loosely on the stepping circuit from a PABX4 group selector but with some modifications to work with a uniselector rather than the 2000 type selector used in the PABX4.
For example, uniselectors don’t have “off normal” contacts (mechanically operated contacts which close when the selector steps off its home position) so instead I’m using the homing arc on the uniselector I’m using for the same purpose. It’s also used to drive the uniselector home at the end of the call.
Oh, and thanks to the asterisk server at the railway having extension 491 configured to dial back through my exchange to ring extension 26, and me hooking outlet 9 on my new junction selector back in to the 50 line pax…
I can now call from extension 25 to 26 by dialling: 50309500491 – which goes through my 50 line PAX to the asterisk (50), back into my pax and back out again to my new junction set (30), back in to the PAX again (9) and then back in to the asterisk box (50) off to the railway (0) and then back through my asterisk server and back into the PAX to ring extension 26 (491) – *phew*
Gloriously pointless, but it yields surprisingly good call quality and not a single pulse was lost!
Automatic Telephone and Electric Company (ATM/ATE) – Adverts
Following on from my post the other week about determining what year my PAX was made, I’ve been digging through old telephony books looking for adverts relating to ATM/ATE. While I haven’t (yet) found any relating to my PAX, I have found some adverts from the same company. So here they are:
From the October 1935 edition of the POEE Journal
From A Handbook of Telecommunication by Bertram S. Cohen published 1946
From Telephony by Atkinson, 1948 edition
From Telephony by Atkinson, 1950 edition
I’ve enjoyed working my way through the 30 or so adverts I’ve scanned so far (you can browse the entire collection here) but now that I’ve started looking, I’m going to have to carry on looking! There must be so much of this material hidden away in books, magazines and journals – overlooked by most people who are more interested in the published articles and the content of the books than the advertising which offset the publishing costs.
So, when was my PAX built?
Since I first got it, I’ve been trying to work out how to tell when my PAX was built. Initially, I thought it was much earlier than it is. My first post here describes it as “1930s” which turns out to be wrong. The initial design of it may be late 1930s, but my example is much later. As far as I can tell, there were at least 3 generations manufactured:
- A cabinet with a “black crystalline finish” – this is the version described in an article from 1938. I’m pretty sure there was a 25 line example of this at Ffestiniog when I collected mine.
- A cabinet with a “grey hammered finish” – wired throughout with silk covered wiring (this is the one I’ve got)
- A cabinet with a “grey hammered finish” – wired throughout with PVC covered wiring. This would be later than mine, and there was certainly an example of this at Ffestiniog.
The company which made it, has had several names, and at least three logos.
- A circle containing the letters ATM, with the company name “Automatic Telephone Manufacturing Company”
- A circle containing the letters ATM, with the company name “Automatic Telephone & Electric Company” (as found on my 50 line PAX, shown above top)
- A circle containing the letters ATE, with the company name “Automatic Telephone & Electric Company” (as found on my 10 line PAX, shown above bottom)
Here’s the timeline my internet research dug up. Most of the links below are from the same site, but that’s only because there isn’t a huge amount of information online about this company:
- 1911 – Automatic Telephone Manufacturing Company established (From Uk Telephone History and History of ATM)
- 1912 – Automatic Telephone Manufacturing Company established (From A history of Plessey, Information & Publicity Services, PTOSL, Beeston. This conflicts with the 1911 date claimed elsewhere, but that may be due to a difference in the definition of “established”)
- 1936 – Company changes name to “Automatic Telephone & Electric Company” or AT&E, keeps the ATM roundel in the logo despite the name change (From History of ATM)
- 1938 – AT&E magazine published, describing the first model of my PAX. The unit is described as having a “Black crystaline finish” – my unit is a gray hammered paint finish so is obviously later (From Private Automatic Exchange Equipments, A new series of designs)
- 1946 – AT&E advert, showing the same logo (ATM roundel, “Automatic Telephone & Electric Company” text) as the front of my PAX (From http://www.gracesguide.co.uk/Automatic_Telephone_and_Electric_Co)
- 1950(?) – Another advert, same logo in use (From http://www.flickr.com/photos/36844288@N00/3726593641/)
- 1951 - An extract from an AT&E brochure, also describing the ”Black crystaline finish”
- 1957 – My 10 line PAX has a stamp inside indicating it’s built to “Diagram S202662/Issue 8″ – my copy of ”Diagram S202662/Issue 8″ is dated 1957. However, this just means it was built *after* the Issue 8 design drawing was released.
- 1961 – AT&E merges with ETL and Plessey (From A history of Plessey and History of ATM - the latter notes that AT&E continued to use the name for a while)
So, based on the paint finish, mine can’t be any earlier than 1951, and based on the company name it can’t be later than “a while” after 1961. Hmm, that’s not satisfyingly accurate enough.
All those dates and still no hard evidence of when my PAX was built. It was at this point, I remembered something from a discussion about relay markings. The 3000 type relays used in my PAXes have markings on the end which tell you useful stuff about any special characteristics the relays have. Amongst the markings it tells you which company built the relay, and (crucially) when!
This extract from Telephony by J. Atkinson (Volume 1, Page 113) explains the markings:
I felt like a bit of a muppet. That’s a much easier way to date my PAX and far more accurate than playing “guess when the logo was used”! So, from looking at the equipment permanently installed in my PAX (rather than the selector cans, which can be removed), I found relays with the following dates:
- 1956,1957 (First 40 line circuits)
- 1960 (Last 10 line circuits. From the looks of the mounting strip, they’re a later addition)
- 1951, 1957 (Ringing, Tones, Misc relays)
Ignoring the 1960s additional line circuits, and assuming that the 1951 relays were a batch being used up (or spares replaced from old stock) I think it’s reasonable to conclude that my PAX was built in 1957. So not quite “1930s” as I originally stated, but still, it was built 54 years ago!
If I take a look at the selectors (which are removable, so unreliable for dating purposes as they could be swapped around) I have dates of 1955, 1962, 1965 and 1969. By fluke, I had arranged the selectors on the shelf in date order! I also note that the very first selector I got working was the oldest example.
While in a new-found-dating-frenzy, I thought I’d date my 10 line PAX. This is a little easier to date as it has had less work done to it over the years. The relays are all dated 1958 or 1959.
With this piece of information, I can deduce that the logo with the ATM roundel was in use from the merger (1936) to some time between 1957 (My 50/7A) and 1959 (My 10/2A) and that the change from silk to PVC wiring also likely occurred at around that time (as my 10/2A is PVC wired)
Fuse Confusion Followup
(click to get a 0.5Mb PDF of the appropriate pages)
I’ve done some reading around on this, and happened to find an appropriate section of “Telephony – Volume 1″ by J. Atkinson (Volume 1, Pages 432-433) which describes the alarm fuses I’ve got on my AT&E PAX.
It doesn’t quite marry up with the information I got through the THG mailing list, so I’m not sure what to trust more – I’m inclined to go with the book as it’s probably more reliable than memory – although I may check with the list to see if it’s a known error in the book, or if it was a case of falible memory.
Perhaps I should check my physics textbooks next, perhaps I’ll turn up a formula for calculating the fusible current for a given diameter strand of copper wire…
The AT&E 10/2 PAX (10 line electromechanical phone exchange) I’m restoring has some interesting fuses in it.
They’re designed so that when the piece of fuse wire blows, the flag pops up to let you know which fuse has blown, and a strip of metal pops down to make contact with a bar running the length of the fuse board. This bar is connected to an alarm circuit. If a fuse blows, the alarm circuit activates and a light comes on to tell you about it.
The idea is similar to the fuses I’m used to seeing on the UAX/PABX kit we’ve got at the railway, although they’ve just got two sprung contacts instead of cool little flags.
I’ve done a reasonable amount of googling for every search term I can think of, but can’t find any information about this particular type of fuse (let alone a source for replacements!)
I assume that the colour of the flag (red, blue or black) denotes the value of the fuse, and whilst there are part numbers stamped on the ends, there are no values. The markings are as follows:
I assume the marks in the Horizontal Slot column are model numbers, but I’m not sure what the “31/n” bit is about, especially as it doesn’t match up with the last three digits of the model number.
So – has anyone got any ideas where I could get some more of these fuses? Has anyone got any ideas what value fuse wire I should attempt to repair (or replace) them with?
Ian came round after work today, to help me unload this from my car (where it’s been since Sunday morning when I bought it) as I can’t lift it on my own!
It’s an ATE 10-2 PAX, which is a 10 line electromechanical phone exchange (lots of buzzing, clicking and whirring bits in there!) – designed for small business/factory use, it was built by the Automatic Telephone & Electric Co Ltd, of Liverpool.
It’s missing its power unit, and only one of the line fuses is intact, but otherwise it appears to be complete.
My plan is as follows:
- Get hold of some diagrams for it
- Build a new PSU for it (probably based around some lead acid batteries and a charger)
- Get it working
- Strip the case down, and have it shot blasted and repainted
- Possibly build a new front door for it out of perspex, so you can watch it do its thing as you dial
- Build a plinth for it with casters so I can move it about more easily
- I’m also hoping to build an appropriate relay set to get it talking to CNET
First things first though, it’s been sat in a garrage for years and is filthy, so my first job is to give it a clean!