Swedish Televerket / Ericsson BC 311 extension phone

[countryman]

I just found a Swedish Televerket / Ericsson BC 311 phone. The internet knows a couple of them, but information is rare. Erel.de (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.

[countryman]

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.

[countryman]

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.

[countryman]

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?

[RB]

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.

[countryman]

This one was 52.38 Euro and it has some loose screws.

[RB]

lol...me too...

[dsk]

It should have an external ringer box too: https://digitaltmuseum.se/021026309182/telefonapparat

https://digitaltmuseum.org/search/?sort=production&aq=descname:%22Bordstelefon%22


dsk

[countryman]

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 :

[FABphones]

Good to see that cradle and handset on the phone   

Screenshot from above link showing 'ringer box' for reference:

[countryman]

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
I'm quite convinced the missing coil might be replaced with a simple 2500 Ohm resistor, if not omitted at all.

[Western Bell]

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.

[Jack Ryan]

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

[countryman]

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.

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.

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.

[Jack Ryan]

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.

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?

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.

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