Norwegian: Elektrisk Bureau 1967

[dsk]

When this one became the only Norwegian standard in 1967, you could get it as a table top, in grey, and you might get a grey plastic "table" to hang on the wall. Youst to choose what you want.

This "ultramodern" electronic EB 1967 was equipped with dynamic transmitter and an amplifier with 2 transistors. Due to the high cost of theese expensive transistors the hoockswitch became extensive, and made it possible to use the transmitter to produce a warbeling beep as a ringing signal.
This model was made until push buttons was introduced as late as 1982.

The rining tone was of a frequency who made it hard to deside witch telephone it came from.

The ren load will vary depending on ringer volume, from about 1.3 to 2.4

[LarryInMichigan]

It looks an awful lot like an Ericsson Dialog to me.

Larry

[dsk]

Larry that's right, it looks identical, because the plastic parts are made in the "same" mold. EB and LME had a close relationship, and the differences are small.  The receiver cap are different, the dial are different, and the plastic part where the the screw to fasten the cover was transparent in Sweden and same color as the phone in Norway.  The main difference are still the circuit  with transistors, dynamic transmitter element = receiver, and no traditional ringer, or as I said in another thread:

The Ericsson Dialogue telephone was made under licence in many countries. Most countries used identical circuits as the swedish one, and the dial was the same with or without lettering depending on local standards. Of course we could not keep everything as standard here in Norway, so our had different caps on the handset, with dynamic transmitter and receiver elements. (identical elements) The transmitter were also acting as a loudspeaker for the electronic ringer signal. With this setup you needed a totally different circuit so it had a complex hookswitch, and 2 of those new expensive transistors for use as a amplifier of the transmitter. In on-hook position one of the transistors made a howl 2500 Hz mixed with the ringing frequency making a warbling whistle. Of course we had to use another dial with the mechanism equal to what the BTMC or Antwerp telephones used from about 1930-ies. None of these had automatic line compensation, just a resistor and capacitor circuit.

dsk

[ma_xyz]

I spend a few weeks in Norway (Narvik). Our hosts, knowing about my "addiction", got a couple of old norwegian phones for me to have something to tinker in case of bad weather - the weather is currently perfect, often sunny and warm - still I found some time to clean up the phones.

One of the phones is a "EB 1967".
It looked very standard from the outside, when I first opened it up I was suprized to not find a ringer - I then found this forum thread which explains everything perfectly - and thanks to another mentioned thread also found the LME Review article about it. A very interesting phone. I cannot test it here, but as everything looks in good shape I assume it would work. Will take it home in a few weeks and test it then.

I have two questions, perhaps anybody knows (perhaps @dsk ?):
- Identifying year of mfg? On the bottom outside of the phone there is printed/stamped: "36 72" - could '72 mean the year of mfg?
- Names for the device?
-- Manufacturer: "EB 1967" or "Dialog"?
-- How did the Norwegian PPT (Televerket?) call it?
-- any Nicknames?

[dsk]

This is a 1967 modell Made W 36 1972, shoud work well in US.  REN load depends on volume settings.
( the  dynamic transmitter /receiver capsules was used as diskant elements by some HiFi freaks)
dsk

[ma_xyz]

Thanks for the info. And the interesting tidbits about HiFi use!
My "homebase" is Switzerland but I'm confident that it will work as well :-)
Michael

[dsk]

I have two questions, perhaps anybody knows (perhaps @dsk ?):
- Identifying year of mfg? On the bottom outside of the phone there is printed/stamped: "36 72" - could '72 mean the year of mfg?

Year 1972 week 36

- Names for the device?

The name used by telephone people an collectors is "modell 1967"  but most people called it "plystretelefon"  norwegian for "whistle phone" because of that terrible ringing sound

-- Manufacturer: "EB 1967" or "Dialog"? 

The Dialog name was never used here, but in cooperation with LME they used the same plastic top, so if one of them got problems with molding, they could help each other.  (Or maybe EB could not/did not want to spend money on a new design)

From 67 to the push button phone was introduced in 1980 you could simply not get a wall phone here! the solution was a wall mounted shelf designed for this phone.

dsk

[Jack Ryan]

The Dialog name was never used here, but in cooperation with LME they used the same plastic top, so if one of them got problems with molding, they could help each other.  (Or maybe EB could not/did not want to spend money on a new design)

Manufacturers never want to change anything as it costs money and reduces profit.

Requests for change generally come from the operating company, particularly if it is a government monopoly or regulated monopoly (like Bell). The telephone company (the government) wants to be seen to be getting something designed to their specification and taste.

The phrase "designed to our specification" is common and ranges from a colour change to a circuit change for compatibility with the local network.

Jack

[dsk]

You are right here!  This phone was designed because the telco (monopoly) did have problems with the standardization of one single lo-cost, but still trust-able phone working on good and bad lines.  The goal to get rid of the carbon transmitter was essential in this.
a look of the circuitry shows that they solved it with extremely simple circuitry, and it may look like a students project bought for "nothing" and the bonus was to get rid of the expensive ringer by making a little more complicated hook-switch and just use the components already in the circuit.  If you try one of these on a short line with plenty of power it gives to loud transmitter signal (high volume). but it still works well on the worst lines we had.

dsk

[countryman]

Interesting circuit. I'm puzzled how it actually worked... the ringing AC was used to generate the whistling sound in both dynamic elements?

[dsk]

A quick translate from a book:   

1) Signal circuit
In fig. 3.20, FIG. 3.18 have been supplemented with features that are specific to this
appliance (or at least less general than the fork circuit
used).
Since the device makes use of transistors, which require dc is
a (two-way) rectifier inserted between the telephone line and the device's signal and
speech circuit.
When receiving a ring signal, ie with the handset on, the amplifier
is switched to an oscillator with a frequency of 2,500 Hz.
The rectified ring signal is not suitable as the supply voltage for the oscillator.
The rectified voltage must be equalized. This is done via the choke (coil
with iron core) L1 and the capacitor C4. The voltage across C4 is the supply voltage for the oscillator. The capacitor C5 in parallel with the winding of the microphone
constitutes the resonant circuit of the oscillator. The frequency of the oscillator is substantially determined by this, but is also influenced by C4, C6 and RI I. Transistor Q1 is the active element of the oscillator. Q2 (and R6) are here of completely insignificant importance, even if it is not completely disconnected.
The strength of the ringing signal, and thus the strength of the tone from the microphone
( "whistling tone") can be adjusted in three stages by the resistors R1, R2
and R3. The varistor RV1 has a resistance that decreases as voltage increases and
does not affect the ring signal any further on
the other hand, it prevents low-energy signals (for example, sending
numerical signals from a parallel-connected telephone) 1 from starting the oscillator.

[dsk]

If we look at the voice circuit, this diagram may clarify.  Here is all the hooks witch contacts just skipped.

To be a little rough with the circuit designers, this could be the Siemens W28 modernized with a transistorized transmitter. 

[countryman]

That's a great explanation. It's a bit tricky to see in the original post how the 2 transistors act together as a two-stage amplifier in off-hook position while Q2 works as an oscillator for the ringtone.
But with the 2 separate diagrams it becomes clear.

Edited for clarification.

[dsk]

I find no better way to show it, and for those who has heard the whistle it is a 2500Hz tone interrupted by the ringing frequency, so it is pretty different from 20 to 25 Hz. A terrible sound, that you can not miss, but it is hard to locate the source of the sound. E.g. if you have 2 lines with equal phones in the same office.

[RB]

An interesting topic, for sure.
I too, have difficulty honing in on the source of those high pitched squealers. lol.
A lot of devices now, use tiny beeper elements to signal.
Not sure who designed them at that freq? musta had great ears!
You can definitely hear it,But it sure makes it hard to pin point which one is crying