Gray Euro Phone??

[Alex G. Bell]

Right.  Here is the circuit, it had two transistors.

Ref:  E. Roth, Fernsprechapparate in der Welt.  p.122

Thanks.  That's more what I would expect.

[Alex G. Bell]

E. Roth's 1970 technical review "Telephones across the World" states that even the Swedish administration did not use the Ericsson Dialog design circuit, but also used their traditional bridge circuit.

Curious.  I wonder why not and who did use it.  Foreign customers?  Private PABX purchasers in Sweden?

[unbeldi]

Here is the original design paper for the tone ringing transistor set:

Wangenstein H., Wessel T. (EB, Oslo): DIALOG with Microphone Amplifier and Tone Ringing.  Ericsson Review, 44 (3) p 98 (1967)

So they did call it a DIALOG, too.   Once a Dialog, always a Dialog, it seems.

[Alex G. Bell]

Here is the original design paper for the tone ringing transistor set:

Wangenstein H., Wessel T. (EB, Oslo): DIALOG with Microphone Amplifier and Tone Ringing.  Ericsson Review, 44 (3) p 98 (1967)

So they did call it a DIALOG, too.   Once a Dialog, always a Dialog, it seems.

Thanks.  I guess so.  I suppose one trade name to defend in court is enough!

[unbeldi]

Looking at the diagram, it seems the ringing alert is actually originated from the microphone, not the receiver element.

[unbeldi]

Somehow, it seems, the idea is reminiscent of the Morris experiment, only ~ten years later (by design).   When originally reading the design paper of the Dialog by Ericsson's people, it already had occurred to me that they were VERY aware of the work at BTL.

[Alex G. Bell]

Looking at the diagram, it seems the ringing alert is actually originated from the microphone, not the receiver element.

That's what DSK said and it makes a whole hell of a lot more sense from a human factors viewpoint. Anyone who has pressed the line switch bar on an Ericofon to disconnect and get dial tone for another call and had a call come in while the receiver was to their ear can truly appreciate why they did this.  It's very very unpleasant!

[Alex G. Bell]

Somehow, it seems, the idea is reminiscent of the Morris experiment, only ~ten years later (by design).   When originally reading the design paper of the Dialog by Ericsson's people, it already had occurred to me that they were VERY aware of the work at BTL.

Probably so.  OTOH the idea for the XB switch migrated from Sweden to BTL. 

But the Morris and previous tone ringer experiments used an acoustic resonator within the base of the set so it seems like it would have been capable of achieving much greater SPLs.  The S1A and W1A tone ringers used on standard analog lines also contain resonator chambers.  Does not seem feasible to do so with a handset transducer, but I have not read the article!

[unbeldi]

Probably so.  OTOH the idea for the XB switch migrated from Sweden to BTL. 

But the Morris and previous tone ringer experiments used an acoustic resonator within the base of the set so it seems like it would have been capable of achieving much greater SPLs.  The S1A and W1A tone ringers used on standard analog lines also contain resonator chambers.  Does not seem feasible to do so with a handset transducer, but I have not read the article!

I think the key to providing enough "alerting potency" is the 2500 Hz frequency.  The Crystal Lake/Morris-type ringers operated much lower, and it was 10 years earlier.

[Alex G. Bell]

I think the key to providing enough "alerting potency" is the 2500 Hz frequency.  The Crystal Lake/Morris-type ringers operated much lower, and it was 10 years earlier.

The S1A is at 750 & 1500.  Not sure how the 2 frequencies are produced by a single tuned circuit.  Perhaps acoustically.  W1A might be the same, don't know. 

There's also a question of how pleasant or unpleasant sounding various frequencies are.

[dsk]

Please listen to this: http://telemuseet.no/wp-content/uploads/1967_eb.mp3

dsk

[dsk]

The Ericsson Review   https://www.ericsson.com/en/about-us/history/sources/lme-review

[Alex G. Bell]

The Ericsson Review   https://www.ericsson.com/en/about-us/history/sources/lme-review

Thanks.  Unfortunately this is in Swedish (I guess).  There is or at least was an English archive on line at one time but AFAIK E-R was not published in English during WW-II.

[dsk]

This is a mi

Thanks.  Unfortunately this is in Swedish (I guess).  There is or at least was an English archive on line at one time but AFAIK E-R was not published in English during WW-II.

It is a mix. e.g. 1967 is in English. 

dsk

[Alex G. Bell]

It is a mix. e.g. 1967 is in English. 
dsk

What is the article about?