UAX13 Telephone Exchange

[Arabhacks]

The reason for a tone generator is that this tone generator produces the tone as well as timing signals for the entire exchange.

And, no, a simple chip can not contend with all of the stray voltages imposed at any time, leave alone a lightning strike, very common when you have thousands of lines to one building.

And, if someone goes off hook and the line finder "bottoms out" this is logged as a "busy fault".

There are normally fewer lines than subscribers, that is a given.

[conceptcity]

It depends on the type of exchange and how it's configured. In the UAX13 here there are 8 linefinders (each with its own group selector) in each A-Unit. There are up to 50 customers connected to each A-Unit. So the answer is 8... however the 50 customers will share their L/F's with incoming junctions from other exchanges.

A meter will step if a customer cannot get dial tone due to all L/F's in use. The telco should monitor this and take steps to remedy if it happens too often!

Cheers!

Rob

[rsp196607]

From one to another, thanks!

A line finder can serve only one line at a time. In an exchange, surely there are much fewer line finders than there are lines. Yet surely any given line has a path to more than one line finder, in order to maximize the probability of that line getting dialtone any time the subscriber takes it off-hook.

To how many line finders does each line have a path? In other words, how many line finders are potentially capable of finding any given line?

[rsp196607]

The things under the yellow cans--were they plug-in or hard-wired?

[conceptcity]

They are nearly all plug in - mainly selectors. There are relays under the cans. The ones that are hard wired are the 'thin' vertical ones at the bottom of some racks (as seen at 0:38 secs) again they contain relays - subscribers line circuits. Also two long thin horizontal strips seen at 2:16 contain misc relays. The selectors were 'plug in' as they needed to be removed if certain adjustments were necessary.

Cheers!

Rob

[slaynt]

I was on Exchange Construction in 1980 and went to evening classes doing the first ever City & Guilds Microprocessor Computer Principles. Then at work installing multiselectors I was wondering why we didn't use microchips to do the same job. Just imagine how frustrated I was when installing a tone generator which must have cost £1000 each when a 20p 555 timer would do the same thing. They retired me age 33 because I had a bad back. And I was more skilled than my EE who was always drunk.

[barryjowett]

Anyone seen my 81's?

[shauntest]

I still remember the smell when walking into my first step-by-step exchange.

[BullfrogFM]

What a sweet old exchange. When I worked for British Telecom in the the 80's there were still several of these switches, UAX 13's 14's in the Oxfordshire area including Burford. I used to do all my testing out to line with a test cabinet identical to the one in the video. The Burford had a really ancient ringing machine which I believe went to the Oxford telephone museum when it was decommissioned.

Thanks for the memories. Former T2A Witney Oxfordshire.

[treborl65]

Fantastic video I guess from a later UAX as its mostly light straw, were was it filmed?. I still work in telecoms for T-Mobile and wish I had captured in film some of the Strowger and TXE2 I worked in years ago. On my desk at work doing faithful service as a bookend I have a 2000 type group selector dating from 1948 (battleship grey) I stole (sorry BT) from one of the exchanges I worked in when it closed late 80's, happy days! Nowadays people ask me what the hell is that on your desk !!

[Tomek1958100]

@treborl65 Strowger DE BEST

[4beatlefans]

OMG did these sounds bring back memories or what... Now; where's my

No.2 and my 9083? Oh yes, still in my Morris Minor van...

[bakelitetelephones]

Fantastic, its good to see and hear Strowger again. I even remember bank cleaning group selector racks as a youth with fond memories :-)

[unlokia]

The Strowger switch contacts need cleaning every few months, as the wear produces minute filings which, if not cleaned up, could lead to shorts and other problems. Also, the majority of open-housing low voltage relays used in telephone exchanges, used to have "bifurcated" (two independant contacts on the end of one strip) contacts for redundancy. If dirt/insects/detritus got trapped between one set of contacts, preventing conduction, the logic is that the other set would still close the circuit!

[unlokia]

Those noises are: 1/ (whining noises) = Ringing generator & cable compressor (pressurises the trunks to prevent ingress of moisture) 2/ "cla-cla-cla-cla-clack" noises are the "Strowger" switches stepping to row/column contact to route the call. There are MANY steps involved in the routing of a phone call on Strowger analogue, and LOTS of noise & wiring (and power required!!!).

[BeachClubMember]

Brilliant, takes you back to the 'good old days' of the 60's..plus trips to Bletchley, Shirehampton and Stone.

Sevenoaks ATE was a great place to work..good view from the windows plus comfortable rest places in the racking!

[tractionman]

Used to change batteries in Uax's.....lousy job !

[JimmyJagg]

Oh, and the loud motor noise is from the ringer machine used for tone generation.

People often used to comment on the noise when they entered the exchange, but after a few years you no longer heard it. I still don't!!!

[d2ohn]

Isn't the loud noise from the compressor?

[JimmyJagg]

You're correct - and so am i! You can hear the ringer machine with it's distinctive 'whine' and it is also possible to hear the cable presurisation compressor with the sort of deeper sounding 'chuffing' noise.

Gawd - sorry that my choice of words is rather heath robinson, a bit like some of the clockwork strowger stuff!!!

[d2ohn]

Thanks for the clarification:-)

I really enjoyed this video, brings back some great memories.

[JimmyJagg]

The background noises are from the two motion selectors stepping up and around to the bank outlets. The noise is actually from the electro magnets pulling onto the armatures.

I have many happy memories from my time in a group switching centre.

Anybody got a video of M.U.G.S. (Motor uniselector group selector) to post on here?

[sp5sjt]

Cudo!! Prawdziwy cymes dla konesera takich cacek :D Daję 5!

[chaudhrysahab]

I am glade we are getting much better exchanges with Routers & switches now.

[carmenlee87]

what are those noises