UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Reply
 
Thread Tools
Old 14th May 2019, 11:37 am   #1
dominicbeesley
Octode
 
dominicbeesley's Avatar
 
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,701
Default Homebrew Strowger exchange

Hello, I know next to nothing about telephones and would like some advice - please go easy on me!

My 4 year old daughter found my box of battered old 746 telephones I acquired over the years and was fascinated by them. She's been (fairly) patiently helping me strip them down and give them a deep clean - filthy nicotine soaked, paint spattered and grimy as they were, truly "mossy".

I've now rigged up a pair in her bedroom with a 9V battery and she loves them. I'd now like to take it to the next step and make them ring and, if possible, rig up a few more extensions and make a mini-exchange. I've not much more than a vague idea of how it all works but would it be as simple as one/two uniselector(s) and a few relays or is it a lot more complicated than that.

I'm thinking something simple that would allow any one out of ten 'phone be able to dial any other which would then ring.

Would making a homebrew strowger exchange be a possibility, a weekend project or a long term labour of love?

Does anyone have ideas where I should start to look for inspiration? I've done some googling and reading about linefinders and allocators but I'm not sure how/if I can do away with them in a simple exchange like this - would it just need a simple relay for each subscriber?

Any ideas or inspiration would be appreciated

D

D
dominicbeesley is offline   Reply With Quote
Old 14th May 2019, 11:53 am   #2
Scimitar
Hexode
 
Scimitar's Avatar
 
Join Date: Oct 2015
Location: Gloucestershire, UK.
Posts: 491
Default Re: Homebrew strowger exchange

Quote:
Originally Posted by dominicbeesley View Post
Any ideas or inspiration would be appreciated
An Arduino and a few relays should be able to handle a job like that.
Scimitar is online now   Reply With Quote
Old 14th May 2019, 12:29 pm   #3
dominicbeesley
Octode
 
dominicbeesley's Avatar
 
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,701
Default Re: Homebrew strowger exchange

Yes, thanks, it's a good idea and I had given that some thought (I've got so many Raspberry PI, Arduino and PIC boards that are begging for a job). But it wouldn't be as much fun, either for me or my daughter but I think a lump of chattering rattling metal would!
dominicbeesley is offline   Reply With Quote
Old 14th May 2019, 1:08 pm   #4
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,224
Default Re: Homebrew strowger exchange

Quote:
Originally Posted by dominicbeesley View Post

I'm thinking something that would allow any one out of ten 'phone be able to dial any other which would then ring.

Interesting you say ten extensions.

See if you can lay your hands on an old BT Minimaster 3 PABX, they were once very popular in offices etc. they support dialling between up to ten extensions, (and two exchange lines).
They are based on an 8 bit processer chip (Z80 I think) but they are full of relays that clatter like good-uns as you dial. A positive advantage in your application!
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 14th May 2019, 1:58 pm   #5
M0FYA Andy
Octode
 
Join Date: May 2007
Location: Preston, Lancashire, UK.
Posts: 1,819
Default Re: Homebrew strowger exchange

Post Office 3000 relays and uniselectors only allowed, none of these new-fangled digits, just the Mk1 used to operate the dials!

Andy
M0FYA Andy is online now   Reply With Quote
Old 14th May 2019, 9:40 pm   #6
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 5,420
Default Re: Homebrew strowger exchange

Hi Dom, there was an article in WW in the 70's that covered the design and construction of such a system using relays and uniselectors for home use.
It should be in one of the online ww indexes.

Ed
Ed_Dinning is offline   Reply With Quote
Old 15th May 2019, 12:13 am   #7
Craig Sawyers
Octode
 
Craig Sawyers's Avatar
 
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 1,812
Default Re: Homebrew strowger exchange

I suppose you guys already know the Strowager story? He was an undertaker in Kansas city. But his competitor's wife was a switchboard operator. So when someone tearfully told her that they needed an undertaker, his competitor got the job.

So Strowager reasoned that an impartial system had to do away with the switchboard, and set about automating it, eventually setting up a company to commercialise his patent, which covered pulse dialling and connection apparatus to route the call.

Craig
Craig Sawyers is offline   Reply With Quote
Old 15th May 2019, 11:06 am   #8
dominicbeesley
Octode
 
dominicbeesley's Avatar
 
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,701
Default Re: Homebrew Strowger exchange

Thanks all,

Ed, good pointer - I've located a couple of WW articles for inspiration

Craig, I knew he was an undertaker - I'd not realised the motivation was to avoid anti-competitive practice!

Now to find some reasonably inexpensive uniselectors and relays...and sneak them past the missus!
dominicbeesley is offline   Reply With Quote
Old 15th May 2019, 5:17 pm   #9
OscarFoxtrot
Heptode
 
OscarFoxtrot's Avatar
 
Join Date: Apr 2011
Location: Edinburgh, UK.
Posts: 666
Default Re: Homebrew Strowger exchange

There is this one:

http://www.samhallas.co.uk/repositor...e_exchange.pdf

as well as the 10-line relay telephone exchange I have attached, which is also available here

https://www.americanradiohistory.com...ld-1980-08.pdf

(note the corrigenda in the following month's issue)

If I may link to another forum, the project has been discussed extensively here

http://www.classicrotaryphones.com/f...?topic=6218.60
Attached Files
File Type: pdf 10 line telephone exchange.pdf (1.40 MB, 32 views)
OscarFoxtrot is offline   Reply With Quote
Old 16th May 2019, 11:21 am   #10
dominicbeesley
Octode
 
dominicbeesley's Avatar
 
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,701
Default Re: Homebrew Strowger exchange

Thanks OFT,

I've had kind offers of uniselectors and relays and some more diagrams so the 1972 article looks like a good starting point. I suspect this will be a slow burn (with a lot of experimenting) while I work all this stuff out...and find space for it!

D
dominicbeesley is offline   Reply With Quote
Old 16th May 2019, 11:59 am   #11
PsychMan
Octode
 
PsychMan's Avatar
 
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,201
Default Re: Homebrew Strowger exchange

I did this a few years back, and used the ringer settings referred to in the comments:

https://www.instructables.com/id/Hac...hone-Intercom/

Essentially using unlocked Linsys voip adapters, one phone rings when the other is picked up

I used 2 Linksys boxes and changed the settings slightly so instead of 2 phones into 1 unit, I have 1 phone in each, and the calls go over IP to the other module / phone. But that was because I was linking 2 distant rooms that happened to have Ethernet..
PsychMan is offline   Reply With Quote
Old 17th May 2019, 1:11 pm   #12
dominicbeesley
Octode
 
dominicbeesley's Avatar
 
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,701
Default Re: Homebrew Strowger exchange

That might be an idea as a stop gap!

D
dominicbeesley is offline   Reply With Quote
Old 22nd May 2019, 7:31 pm   #13
duncanlowe
Hexode
 
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 398
Default Re: Homebrew Strowger exchange

I once was loaned what was effecively a 10 line PABX as far as I woked out. One call at a time. It was loaned to show people the principal of how pulse dialling worked. I only ever set it up with a few instruments as a demonstration. The box itself was pretty small, about the size of a milk crate, presumably meant to sit on a wall somewhere. I have no idea if it could take a public line too. You might get lucky and find something like this, it would be ideal. Unfortunately I have no idea what it's proper name, manufacturer or anything like that so searching could be tricky. The person who loaned it to me worked at GEC / Plessey telecoms in Coventry so may have been something they had made in the past (he worked on System X).
duncanlowe is offline   Reply With Quote
Old 22nd May 2019, 8:58 pm   #14
AC/HL
Moderator
 
AC/HL's Avatar
 
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 7,200
Default Re: Homebrew Strowger exchange

That would be the Plessey 10/1, ten extensions one speech path. There was also a 15/2: https://www.britishtelephones.com/ericsson/pax10_1.htm
__________________
Bill, BVWS member
AC/HL is online now   Reply With Quote
Old 23rd May 2019, 10:23 am   #15
dominicbeesley
Octode
 
dominicbeesley's Avatar
 
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,701
Default Re: Homebrew Strowger exchange

Thanks both, that looks interesting - though I'm now set on something uniselector based...just because!

D
dominicbeesley is offline   Reply With Quote
Old 23rd May 2019, 4:21 pm   #16
duncanlowe
Hexode
 
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 398
Default Re: Homebrew Strowger exchange

Quote:
Originally Posted by AC/HL View Post
That would be the Plessey 10/1, ten extensions one speech path. There was also a 15/2: https://www.britishtelephones.com/ericsson/pax10_1.htm
Similar but not one of those. It definitaley had some kind of uniselector that rotated as you dialled, not just relays. It was also unvented and a slightly different shape, and in GPO beige. But now I know they are called PAX not PABX I'll try looking further.

EDIT: I reckon it was one of these (ETL plessey apparently):

http://www.aeolian-hall.myzen.co.uk/atepax10.jpg

EDIT again:
So not a 10/1 but a 10:
https://www.britishtelephones.com/ericsson/pax10.htm

Last edited by duncanlowe; 23rd May 2019 at 4:30 pm.
duncanlowe is offline   Reply With Quote
Old 24th May 2019, 1:49 am   #17
jjwayle
Tetrode
 
Join Date: Jun 2009
Location: Bromley, London, UK.
Posts: 56
Default Re: Homebrew Strowger exchange

I'm lucky enough to have both the 15 line version as well as the 10 line version up and running in our little museum of all things telephony!

The 10 line version arrived with a very rusty lid so i cut it out and fitted plexiglass and LED strip light so people can see it working on the open days for our set up and our garden railway.

Once the strowger bug bites, it bites hard, we have another 50 line PAX, a GPO PABX 5 (5+20 exchange) and two little demo units.

Its so good to have stuff up and running and anything to encourage the younger people (does 34 years old make me young still?!) to get interested is a good idea-having stuff working really helps!

Jason
Attached Thumbnails
Click image for larger version

Name:	IMAG0183.jpg
Views:	64
Size:	76.1 KB
ID:	183734   Click image for larger version

Name:	IMG_1508.jpg
Views:	61
Size:	84.4 KB
ID:	183735  
jjwayle is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 8:33 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.