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Magneto Elektrisk Bureau 1918 (made 193x)

Started by dsk, April 20, 2014, 03:00:42 PM

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This one was known as "mellomstasjonsapparat" ~mid line subscriber. It has a manual selector for calling up or down the line. When going off hook the next stations were only connected to the ringer.

This is a version of the first standardized circuit by our "ma Bell" Telegrafverket. The phone are a pretty late version, but still sidetone and cutout button to short everything except the receiver to get better sound.



Here is the simplest circuit of the 1918. This was the standard version with no selector switch as the phone pictured.


More info from a book and some pictures. The table top was made in several designs between 1918 and 1934 but the wiring diagram remained. Ringer 2 000 ohms.


Hey, DSK, That wall phone looks a lot like the one I have.
Nice phone, but what a monster!
It had been stripped by former owner, or CO.
Was supposed to be a convert to CB with a dial, but was never finished.
I had to completely rewire it, so I went back to LB, and removed the dial.
I would like to trade it for a smaller one, but those are expensive here.


Took a new picture of the diagram, and got ssome help to transform it and here is the before and after pictures:

The phone itselves is the typical 1918 diagram, + the 2 line selector switch that makes the line 1 be the normal one, and line 2 is across the ringer. (The ringer is shortened when cranking)  Turning the switch to the oposit position line 1 and 2 swithch connections. so you may ring indirection 1 or 2, and the oposit direction will not hear anything.


I have observed that schematics in the way you use to have them are much more easy to read, so I have tried to make a version I like better, just for understanding the original better. I took the last magneto version made by Elektrisk Bureau, and modified that diagram.
If you take that modern 1953 version and add a switch then you got this, but with anti sidetone.


Made it even simpler, (I believe):


You did a great job to make the old diagram readable! Those often were more constructional plans than schematics that allow getting an idea how things actually work. All the long and crossing lines make it very hard to to see the essential principle.