The Return of the Rotary Telephone

[cadman]

SxS

Funny the topic of switching came up... I've always wanted to build a small-scale Strowger system but parts are expensive, tough to find (other than the more common selectors), and the wiring can be a nightmare. By chance this opportunity presented itself, completely assembled, and it had to come home! It includes a line-finder, a digit absorbing first selector (plus std selectors) and the required connector to provide for 7-digit dialing.

The person that built it did a top-notch job, but a little additional wiring would make it more versatile. That said, after some tweaking, the sucker works! -C

 

[gusherb]

Now that is cool!!

I wish I could go back in time and experience the PSTN before it went all digital I hear it was FAR more interesting when making a call due to all the buzzes and clicks during call setup etc. None of the elders in my family ever paid attention to this kinda stuff, except my mother remembers the "all circuits are busy now will you please try again later" (or just a reorder tone) on days like Mothers day.

Our CO has been digital since it was built in 1977 (Siemens EWSD switch), and the rest were probably converted over in the early-mid 80s.

 

[iej]

Yeah, I'd say the old network was far more interesting than modern digital switches although some of them have their quirks too, but certainly no buzzes or clicks.

That step-by-step demonstration unit is pretty cool. I've only ever seen and used one in the Science Museum in London.

 

[davetranter]

Memories, memories

Interesting thread for an Ex-GPO Telephone Engineer.

Iej is almost right in saying that there was a direct metallic connection for local calls. The windings of the 'First' (or was it 'Final'??) selector 'A' relay acted as a sort of isolation transformer, providing a guaranteed bandwidth of 300Hz-3400Hz, but usually plenty more. Inter-exchange and long-distance calls were usually multiplexed in some way, and the bandwidth was strictly limited to 300-3400Hz.

Switching systems included TXS (Strowger, various manufacturers) .... TXK (Crossbar, mainly Ericsson) ... TXE (TXE2, no idea who made this equipment, but this was the stuff with banks of reed relays.... and TXE4, which was largely solid state switched) .... TXD (Digital, Marconi System X and later (just after I left the firm) System Y).

I worked there long before the Internet was dreamed up. Data circuits were either dial-up (up to 1200 BPS) or 2-wire leased-line (up to 2400 BPS) or 4-wire leased-line (up to 9,600 BPS, or 19,200 BPS with special modems). Those were the days!!!!!

There was a (phenomenally expensive) 2,000,000 BPS system which required the laying of specially screened cables, but few could afford this!!

There was also the TELEX network, which IIRC ran at 75 Baud, and a teleprinter network used by the bookmakers which ran at 50 Baud. High speed indeed!!

Hope this may be of some interest.

Dave T

P.S. I have a couple of 'bakelite' telephone instruments (GPO '300' Series) and a couple of Strowger selectors and Uniselectors, but the selectors don't have the contact 'banks', so I'm unable to make a working 'micro-exchange'...

P.P.S. I also have a bunch of spare parts

 

[iej]

@davetranter The codes used for exchange types in the UK seem to be (quick Google found these).

Crossbar:
TXK1 = Plessey 5005A (some made under license by GEC)
TXK2 = 4-wire version of the same.
TXK3 = A version of the French designed ITT Pentaconta made under licence by STC (apparently was the only type of exchange used in Northern Ireland)
TXK4 = 4-wire version of the same.
TXK5 = Ericsson ARM (tandem / international gateway)
TXK6 = Ericsson AKE (tandem / international gateway)

Seems the Ericsson gear was only used for international gateway purposes in the UK.

Electronic / Relay:
TXE1 = Consortium of basically the whole UK telecommunications sector + GPO.
TXE2 = Plessey Pentax
TXE3 = same consortium as TXE1 (just a reduced cost and updated version)
TXE4 = STC built just a development of the TXE3
TXE4A = Same again, just tweaked and updated.
TXE4E = Further enhancement (unknown if it was ever used as it was released in the 1980s)

Digital Exchanges:
System X = GPT/Marconi system X
System Y = Ericsson AXE
UXD5 = No longer used, small rural exchange made by Plessey based on the Monarch PABX office system.

---

Over here in the Republic of Ireland:

First Generation:
Stronger Step-by-step (various suppliers)
Siemens Rotary.

Second generation (from 1957)
Exclusively Ericsson Crossbars manufacturers by LM Ericsson in Athlone, Co. Westmeath.
ARF - Large exchanges used in towns/cities
ARM - Tandem / trunk exchanges.
ARK - Remote concentrator exchanges used locally and parented by ARF or ARM major exchange linked with Multifrequency R2 signalling.
ARE11 and ARE13 were computerised crossbars where registers and markers were replaced by computer technology.
AKE - further advance on this.

Digital from 1979 (mostly from 1980/81):

Two suppliers won the tender for a "type a" and "type b" digital switch in Ireland to ensure competition:

Ericsson AXE
Alcatel E10B (now known as Alcatel 1000-E10 in its current versions) - Actually the world's first commercialised TDM digital switch. Also used extensively by France Telecom/Orange.

The Alcatel E10B was originally manufactured under licence from CIT-Alcatel in France by a company called Telectron which was a division of AT&T oddly enough. They closed down and manufacture was moved to a joint venture between Telecom Eireann and Alcatel called "Telecom Alcatel" rather unimaginatively.

There was an Alcatel R&D centre in Bandon, Co. Cork (quite a rural spot) well into the 2000s. It mostly seemed to support and develop software for Telecom Eireann's fleet of Alcatel switches.

Ericsson has quite a big presence here due to the 1950s-90s legacy as a key supplier to Eircom / Telecom Eireann. It still employs about 1500 people in two divisions here, mostly now software R&D for interactive services, but in the past it was mostly providing support for AXE switching systems. At one stage Ericsson Ireland had a 'university' for switch engineers from all over the world to train them up on AXE.

 

[sudsmaster]

I had an old 500 with a metal dial ring... but gave it away about 30 years ago. I had discovered that there was no way to get it to ring on modern telephone lines. I still have a plastic version, which someone converted to a somewhat stylish black and white by swapping out the black and white components between two phones. Somewhere. It didn't occur to me at the time that there would someday be converters to allow conversion of the rotary pulse dialing to tone dialing, and the conversion of the line ring signal to one with enough power to rind the bells.

I may still have an all black plastic 500 as well... somewhere...

Realistically, I don't think the sound quality on a modern cordless phone (I use Panasonic) is all that bad. Although the sound quality on digital answering machines is vastly inferior to those that used old recording tapes. But the tape based answering machines break down eventually, whereas the crappy digital ones just keep on going, rendering calls and music unintelligible forever. Speaking of which, one used to be able to save filled up incoming answering machine tapes for a record. With digital, there's no convenient way to archive old messages, you just have to delete them. Although, with Ooma, one can keep old messages online for what looks to be forever.

 

[iej]

I forgot about answering machines. We used to have a rather cool Sony one when I was a kid (tape based) and it lasted for years.

It was a Sony ITA 550. Quite a cool machine for the era it came from, late 1980s I think. Around the time that Sony was where Apple is now in terms of gadgetry.

It had two micro cassettes and you could do all sorts of really quite voicemail-like things when you called it remotely using touch tone. Like you could play, rewind, fast forward, change it from on/off answer/announce only or leave a voice memo for someone. I think it could even call you at an alternate number with your messages.

It became obsolete when the phone company started including free voicemail.
I have to say though I prefer modern voicemail to an answering machine. My landline messages are delivered straight to my email and an app on my iPhone. So, I can just archive MP3s if I particularly wanted to keep something.

 

[gusherb]

Rich

Panasonic cordless phones (the more recent models) have the best sound quality of any cordless phone out there. I have three sets and they match or beat the sound quality of my vintage phones depending on the condition of their transmitters/receivers.

My absolute best phone for sound quality is actually a Yealink IP phone that supports HD voice. It has an extremely good speaker in the handset and even just ulaw sounds very rich and clear on it. Haven't had an actual HD/G.722 call on it yet but im sure that sounds like the person is in the room with you.

 

[iej]

I'm using a Panasonic VoIP setup with a normal wired handset on the desk phone which is the DECT base station and then we've a few cordless extensions scattered around the house.

The sound quality is outstanding and you can also use all the extensions independently. So if I'm on the phone and someone else uses another extension it just works and the outgoing Caller ID is the same.

If someone calls all the free extensions ring and you hear and see call waiting info on the busy one.

I can transfer to any extension or any dialable number as if it's part of an office phone system as it's on a hosted PBX.

It's also got proper music on hold from the server and the voicemail is extremely sophisticated.

Calls are very cheap and I'm paying significantly less than for a regular landline yet it's vastly more sophisticated and you can configure everything online.

POTS is extremely obsolete when you see what a decent VoIP service can do, especially in a SoHo environment.

The Siemens Gigaset range is also absolutely top notch in terms of sound quality in my experience.