I just found a Swedish Televerket / Ericsson BC 311 phone. The internet knows a couple of them, but information is rare. Erel.de (http://www.erel.de/INH/20/2040311/index.htm) (Ralf), a German collector has some of them on his homepage, and even a diagram. Unfortunately, all these phones seem to have undergone massive modifications - and so does mine :(
I post this in the "Restoration projects" forum, hoping I will be able to restore it to it's original function some day.
As far as I understand now, this phone is a basic private branch exchange. I worked as a master phone on an automated office line, and could call it's "slave" like a LB system. It could also connect the slave to the office line.
There are several very unusual detail on this phone that I'd like to share. I'll create followup entries with pictures for each of them. Any ideas and discussions are welcome!
First a general view of the phone. It does not look too bad at first glance. The bakelite handset seems original, while versions with metal handsets also exist. The shell has been spray painted in light grey - not original but not the most ugly job though. The brass colored fingerwheel and dial housing look original, so does the unusual indicator signal on top.
Opening the bottom plate shows a different picture. These parts look like from 50/60/70ies German phones cobbled together :(
Someone wanted to make this a "working phone" and either the original innards were missing or the knowledge how to use them.
First unusual thing is the dial of this phone, marked L M Ericsson Stockholm 176858, and I do not mean the swedish numbering on the fingerwheel. Having a closer look, this one does have 2 sets of contacts like any dial - but the shunt contact does not shunt. It is closed in the normal position and opens only when the third finger hole (numbered 2) passes the finger stop. I have never seen or heard about such a function?
The arrow in the picture shows the tiny "cam" that lifts the lower set of contact when passing by. The function of the pulse contact is normal.
The magneto is not switched by a mechanism moved by the crank shaft. There is a centrifugal switch on the upper (actual magneto) shaft. The magneto windings are shorted out in normal position. The crank turns somewhat hard due to this. First when up to speed, the centrifugal switch releases (can see an arc!) and then the crank turns easily!
On the other side of the case there are 2 big relay coils, operating a signal element and 2 switches. Someone wired the coils to the magneto! They should be operated when the slave phone is in use, switching off the ringer and indicate a busy line on the signal. Unfortunately, any original wiring is cut off flush.
Third unusual feature is a large induction coil sitting inside the magnets of the magneto. No voltage is induced here, so I assume it is there because the space was available? The body of the coil seems to be black painted wood, filled with iron (?) granules to increase the inductivity. The resistance of the single winding is about 100 Ohm. Such a coil is shown in the diagram on erel.de, but I'm not sure about it's purpose. The second (1000 Ohm) induction coil shown there is missing. My first thought looking at the diagram was that these were 2 windings of the same coil, like normal, but possibly they aren't?
Interesting config indeed!
I would like to know more about it.
It seems like it led a dual life.
I have been looking for a phone shaped like that. But they are priced higher than Trumps opinion of himself. :(
This one was 52.38 Euro and it has some loose screws.
lol...me too...
It should have an external ringer box too: https://digitaltmuseum.se/021026309182/telefonapparat (https://digitaltmuseum.se/021026309182/telefonapparat)
https://digitaltmuseum.org/search/?sort=production&aq=descname:%22Bordstelefon%22 (https://digitaltmuseum.org/search/?sort=production&aq=descname:%22Bordstelefon%22)
dsk
Thank you, that makes sense. Erel.de has a pic of the lower compartment, showing a ringer with 2 gongs and an extra coil. That might be the missing 1000 Ohm coil. I wonder what I could use as a replacement?
The second ringer drawn in the diagram must be in the subset.
Picture fromhttp://www.erel.de/INH/20/2040311/20403115.jpg (http://www.erel.de/INH/20/2040311/20403115.jpg) :
Good to see that cradle and handset on the phone :)
Screenshot from above link showing 'ringer box' for reference:
Quote from: countryman on November 11, 2019, 08:03:46 AM
the shunt contact does not shunt. It is closed in the normal position and opens only when the third finger hole (numbered 2) passes the finger stop.
It begins to dawn on me that the dial might be just out of alignment - the ring with the cam has spun on the shaft. It should lift the shunt contact in normal position!
I also found the diagram of a BC 310 version of this phone, a simple automatic desk phone:
http://www.erel.de/INH/20/2022310/index.htm (http://www.erel.de/INH/20/2022310/index.htm)
I'm quite convinced the missing coil might be replaced with a simple 2500 Ohm resistor, if not omitted at all.
IIRC, the externally linked images in replies #8 and #10 will not be seen if the URL changes at anytime in the future and at that point this discussion will become meaningless to anyone reading this topic after that. Could someone or a mod please add the images as jpeg attachments? I can't do that from my phone.
I'm getting a bit lost in the discussion here.
The phone looks like an intermediate phone to me based upon the CL 500. I don't actually know what a BC 311 is but it doesn't seem to be an intermediate phone ID. Is it an Ericsson ID?
It is a CB telephone that has a bell within but also has an external bell so that both exchange and extension rings can be heard.
Where did the circuit 2040311s.jpg come from?
I don't see a single inductor in that circuit – I see a side tone IC, a magneto and an indicator.
Thanks
Jack
Quote from: Jack Ryan on November 11, 2019, 08:28:51 PM
The phone looks like an intermediate phone to me based upon the CL 500. I don't actually know what a BC 311 is but it doesn't seem to be an intermediate phone ID. Is it an Ericsson ID?
Thanks for the tip Jack - I will study the Ericsson phone you mentioned. BC 311 is what is written on it. It might be a label given by Televerket, the swedish phone co.
QuoteWhere did the circuit 2040311s.jpg come from?
I don't see a single inductor in that circuit – I see a side tone IC, a magneto and an indicator.
The circuit diagram is taken from Ralf's linked page Erel.de . It was my thought, too, that I see a sidetone IC. But what I found was a single inductor with a resistance of 100 Ohm.
I linked to Ralf's photo and the other circuit for copyright considerations. It's also a long time website so hopefully will be visible for a while. I'm hesitant to copy and re-publish other people's stuff without asking, while linking should be OK.
Quote from: countryman on November 12, 2019, 12:15:58 AM
Thanks for the tip Jack - I will study the Ericsson phone you mentioned. BC 311 is what is written on it. It might be a label given by Televerket, the swedish phone co.
Yes, I think that is the case.
Quote
The circuit diagram is taken from Ralf's linked page Erel.de . It was my thought, too, that I see a sidetone IC.
Is it? The second circuit comes from erel.de (the BC 310 - again, not an Ericsson number). Where did the attached circuit come from?
Quote
But what I found was a single inductor with a resistance of 100 Ohm.
Intermediate phones often have an exchange hold function that is usually implemented with one coil of the ringer. It is possible a separate inductor was used. I have never seen one without an IC.
Quote
I linked to Ralf's photo and the other circuit for copyright considerations. It's also a long time website so hopefully will be visible for a while. I'm hesitant to copy and re-publish other people's stuff without asking, while linking should be OK.
I am also hesitant to copy and paste - the proper protocol is to link. The trouble is a lot of WEB sites are disappearing - even some that have existed for a long time like s-storbeck.de. Sometimes they are not on archive.org so they are lost.
Jack
with that circuit I broke my own rule and copied&pasted it right away. Here's the link: http://www.erel.de/INH/20/2040311/index.htm (http://www.erel.de/INH/20/2040311/index.htm)
click on the flag "Schaltplan". Thanks for reminding me of that missing reference.
I'll try to fix the image issue in my earlier posts.
Quote from: countryman on November 12, 2019, 02:48:27 AM
with that circuit I broke my own rule and copied&pasted it right away. Here's the link: http://www.erel.de/INH/20/2040311/index.htm (http://www.erel.de/INH/20/2040311/index.htm)
click on the flag "Schaltplan". Thanks for reminding me of that missing reference.
I'll try to fix the image issue in my earlier posts.
Thanks, I see it now.
Regards
Jack
Looking at the diagram once more. What type of "slave" set (extension) would be used here? A dial phone would work, but could not call the "master". A magneto phone would send ringing voltage down the office line when cranked with the master switched in bypass, the position shown in the diagram. That was never a safe practice on automated exchanges, let alone VOIP routers...
I'm still wondering about the original setup.
That's a cool instrument! Looking forward to restoration progress pics :-)
Quote from: countryman on November 12, 2019, 07:15:48 AM
Looking at the diagram once more. What type of "slave" set (extension) would be used here? A dial phone would work, but could not call the "master". A magneto phone would send ringing voltage down the office line when cranked with the master switched in bypass, the position shown in the diagram.
On erel.de it is mentioned that the extension would also use a magneto: "Die Endstelle wird per Kurbelinduktor gerufen, diese verfügt ebenfalls über einen Induktor zum Anruf der Zwischenstelle." ("The end station is called by magneto, the end station uses also a magneto to call the intermediate station.").
I'm not sure about that but probably some choke-inductors/highpass circuit would protect the exchange side, also mostly the power would be consumed by the additional ringer in the loop shown on the diagram at right?
It was pretty hard to kill an exchange - they were quite robust.
If you look up the Bellset No 20 (N520) on Bob Freshwater's WEB site it will give you lots of connection information. Follow the N diagram links to get the full picture.
The extension telephone is basically a normal common battery telephone with a magneto added. The images I have posted are of an intermediate extension used by the PMG in Australia and its circuit diagram.
Intermediate systems made by (Swedish) Ericsson and also made by German manufacturers worked on the same principal.
Regards
Jack
Here is what looks like another intermediate set and an intermediate switch.
Jack
Thanks for the assistance! I managed to fix the dial meanwhile. The ring with the cam rotates on the shaft after loosening the screw. I also needed to adjust the finger stop, which limits the travel of the finger wheel in the normal position. Now both contacts do what they should.
Did this dial design have equivalents on the international markets?
I can see sending ringing voltage back to a mechanical exchange wouldn't do much harm besides a possible "surprise" for a lineman. But how about electronic PBX?
Quote from: countryman on November 13, 2019, 01:02:58 PM
Did this dial design have equivalents on the international markets?
Do you mean was it
used on the international market? Yes
Do you mean was it
licensed on the international market? Yes, although one licensee, EB, apparently didn't like it and made some modifications.
Quote
I can see sending ringing voltage back to a mechanical exchange wouldn't do much harm besides a possible "surprise" for a lineman.
No more so that if the line happened to ring while the lineman was stripping insulation with his teeth.
Quote
But how about electronic PBX?
I don't think their usage overlapped - in any case, I don't remember ever coming across a case where an intermediate phone was used on a PAX or PABX although one could be used as a secretarial set.
There were alternative intermediate telephone systems that used battery ringing (a button and a buzzer) - the PMG used both. There were also specially designed secretarial sets that were functionally similar for use in an office environment.
Jack
The dial seems to be referred to as "RG 112" in the Ericsson documents I found, but I don't get any further than that...
In fact it would not make sense to operate that setup behind a PBX of any kind, but I think of doing so for demonstration.
I have looked at the Elektrisk bureau copy some years ago, the phone was used on the POTS here. The problem with the dial was the cham did not always release in reverce and sometimes it did break the line. At that time it was repaired by cleaning and oiling.
dsk
I got the dial eventually fixed. The ring with the cam needed adjustment, and also the finger stop. It's underside doubles as a stop defining the finger wheel normal position, and that was off, too.
I have not worked on the phone's missing internal wiring yet.
Thinking it over, this setup would be great to demonstrate magneto phones and connect them to POTS or VOIP lines. The magneto extension could call this intermediate set, where an "operator" would dial the number and make the connection.
Still there is the issue with magneto voltage possibly traveling down the line.
I wonder how serious this issue is? Is there any way to prevent possible damage to modern electronics in a PBX or VOIP interface?
These deal with 48V DC and ringing voltage themselves, so might even have enough internal protection?
Has anybody ever killed such a device with external voltage and cares to report?
That would depend entirely on the device.
If it had protection built in, no prob.
If no protection, poof...
If protection switched in and out, all bets off.
IMHO, of course ;)
It is made for equipment without electronics, so I would have configured it different, e.g. a third wire for the intercom signalling.
dsk
I was lucky and found a fragment of a similar phone for parts. I now can replace the terminal block, the ringer and the contact for the push button on top. Also, the damaged base can be replaced. The old one had the ringer mounting lugs and the threaded spacers for the gong and the terminal block ripped off.
The red fragment is a funny thing, it resembles other old metal phones that were "refurbished" for the antique market as I mentioned here (http://www.classicrotaryphones.com/forum/index.php?topic=23360.msg234245#msg234245).
(http://www.classicrotaryphones.com/forum/index.php?action=dlattach;topic=23360.0;attach=215118;image)
(http://www.classicrotaryphones.com/forum/index.php?action=dlattach;topic=23360.0;attach=215120;image)
This shell has not only been painted red with industrial grade paint (hard to remove), but also must have been sandblasted before. It has a cradle with a fake, functionless gong. Inside the shell there only was an induction coil with 2 windings dated 1940. I wonder who did this...
I plan to take the cradle off and use this shell with the damaged base part as a subset, containing the second ringer and a battery box. I also think about a protective circuit to allow the operation on a VOIP terminal. Then this intermediate set could act as a stylish interface to demonstrate magneto phones...