Monday, March 23, 2009

Rikstelefonen Type E.B. 21 Telephone

Some time ago, one of my relatives brought this wall-mount telephone back from Norway (it had been in the Oslo apartment of my step-mother's parents from the mid 40's until 1980), and he asked me to take a look at it to see if it could be made to work on the American phone network. (He'd be happy just to hang it on his wall, even in a non-working state, but a working phone would be so much cooler!)


The only identifying labels on the telephone are "Rikstelefonen" on the front (just below the dial), and a sticker on the back panel that states, "Type E.B. 21". Given that the phone came from Norway, I'm assuming that "E.B." stands for "Elektrisk Bureau," the Norwegian telephone manufacturer.


Inside the telephone was a dangling wire (with a spade connector) from the dial assembly and a nine-terminal terminal strip. Before I tested the phone, I would first need to reattach this wire. But to what? The dangling wire clearly needed to be attached to the terminal strip, but the terminals were labeled with cryptic markings such as La, EK, Lb, ET, T, and M. Which terminal took the wire, and which terminals should I connect the Telco line to? I had no idea.

(The large light-grey boxy thing with 2 terminals on the back panel is a 2uF capacitor)

After much fruitless searching on the web for information about the phone, I finally bit the bullet and drew a schematic by tracing out the wiring. From that exercise, I discovered that the dangling wire was attached to the dial make-break switch. Clearly it needed to be in series with the telephone line (so that it could pulse the loop-current during dialing). But...I still didn't know which terminal should it go to.

A couple of members of the "Telephone Collector's International" mail-list helped put me on the right track. I'd noticed that two terminals, La and EK, were jumpered together, and that one side of the ringer attached to the EK terminal. Someone mentioned that often the ringer was attached to a ground terminal, and that, for "straight-line ringing" it would be jumpered to one side of the line.

This correlated well with what I saw. 'EK' must be the ground terminal, and 'La'...the 'a' side of the line!

So if La was one side of the telco line, then Lb must be the other side. But nothing was attached to this terminal. Hmmm...probably the dangling wire had been attached to the Lb terminal (along with one of the telco's line wires), and it had fallen off sometime after the phone was removed from service -- the Lb screw had been loosened (I assume to remove the Telco line), but not subsequently retightened.

I connected the dangling wire to Lb, then ran wires from La and Lb to my telephone line. Now was the moment of truth! I took the handset off-hook, and...dialtone!. I dialed my number from another line, and the ringer rang! Upon answering, I realized I could both speak and hear, so the handset was working (although I didn't check levels). And finally, I dialed another line using the (weirdly numbered) dial, and the other phone rang. Everything worked: handset, ringer, and dial!

So the job's almost done, and then I'll return the phone to my relative. But first, I need to replace the handset cord (it's severely frayed), and get a line cord with a modular plug on the end. But once that's done, "Rikstelefonen Type E.B. 21" should be ready for prime time.

(A quick note about the dial. It's numbered backwards from the American dial (with the exception of 0), so one way to dial a number in the U.S. is to count "finger holes" counter-clockwise, rather than use the printed numbers.)
(Oh, those Norwegians!)

And here's the schematic that I drew. I believe it's correct -- I checked it against the schematic I scribbled into my lab notebook, but it hasn't been rechecked against the actual wiring. So use at your own risk!
(Click on image to enlarge.)

Some additional information just received via the "Telephone Collector's International" mailing list...

From Roger Conklin:
According to the book Telefonappater i Norge 1880-2000 page 62, this telephone was manufactured by Elektrisk Bureau from 1921-1924. This book was published (in Norwegian) by Norsk Telemuseum, Oslo in 2000. It describes the telephones in that museum which my wife and I had the opportunity to visit several years ago. I bought a copy of this book at the museum during that visit.
And here's a schematic from a different Elektrisk Bureau phone (original photo taken by Harry Smith and posted here on the TCI photo site. I've used Photoshop to do some keystone correction of Harry's photo, and I've also added some annotation to clarify some of the original schematic symbols).
(Click on image to enlarge.)

Note the differences between his phone and mine: The La to EK jumper is not done on his terminal block (as it is in my phone), but instead it appears to be done in the plug (if I'm interpreting the round symbol on his schematic correctly -- but perhaps that's the wall terminal? Don't know...). (Per Steph Kerman on the TCI reflector, wall-mounted phones (such as the one I'm working on) typically had this strapping done within the phone itself, while desk-top units had the strap inserted at the wall terminals.)

Also, in my phone the two switches within the dial mechanism are not electrically isolated (as is implied by Harry's schematic), but they share a connection (the Brown wire shown in my schematic connects to both switches).

But other than that, the two schematics are quite similar (except for wire color differences).

6 comments:

tur said...

The telephone is a 1924 model based on an older WE design.
This thelephone has been modified later, (it was commonly done when the problems with the carbon transmitter happend, due to the hanset hanging on the left side of the phone). The Oslo and New Zealand dial is typical. The rest of the world uses other dials. Sweeden has their own.

tur said...

The dial is a later dial, you will not ruin the phone by renumbering the dial.
The text in the wiring diagram / terminal block:
T: Telephone (receiver) M: Microphone
EK: Ekstraklokke (Extra ringer)
Strap is used when no extra ringer needed. ET: Ekstra telefon (Extra receiver) La / LB (ring / tip)

Jeff said...

Tusen takk, tur! (Just thought I'd try out two of the four Norwegian words I know.) Many thanks for the information!

tur said...

Just nice to be able to help.

The dial is from a 1953 model seen and heard at this page:
http://www.telemuseum.no/joomla/index.php?option=com_content&task=view&id=448&Itemid=105

This dial has a common wire for the circuit making the brakes, and those who shorts the transmitter and receiver.The one who shorts the receiver opens last when dial stops.

The dial is based on a W.E. design, and may be replaced by a WE dial.

tur said...

You could Print this out, cover with adesive transparent plastic and replace the Oslo Dial numbers with the std numbers.
Remove spring round center label, unscrew dial, unscrew half ring holding enameled number ring, put in the home-made, replace in reverce order!
Look at:
http://img.photobucket.com/albums/v480/dsk/Telephone/ElektriskBureauDial1934-1967_.jpg

Kabel

tur said...

I have experimented a lot the last years, and you may buy a dialgizmo, set it for reverce dial and just hook the phone up on a normal line, or even to a analg telephone adapter or skype-box. Lift off the handset,get the dial tone, dial and you hear a little beepfor each digit, and thats it. theold transmitter element may give a bad sound quality, taking it out, rolling it forth and back on an uneven surface like corrugated cardboard will shake the carbone granulate to and make itwork a little bit better.