Siemens & Halske ZBSA11

[dsk]

I got this phone from a friend, I had a field exchange he wanted, and he had an extra of these. Lot of tear and wear, but it works, and I feel it has a story to tell, so I keep it in this condition.

I have tuned the dial, and added a colloid cone one the transmitter. During its long life it  has got a new capacitor, and probably new cords. The finger-wheel is painted, and I did fresh up the center plate.

The bottom plate is missing, but my friend has found on in his spare part box so that problem is solved, I just have to pick it up next time I go to our summer cabin.


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[HarrySmith]

Nice one! Congrats!

[.....]

Wow, that dial is very similar to the Strowger dial.

[HarrySmith]

I don't think it is similar to a Strowger dial, I think it IS a Strowger dial!

[.....]

I don't think it is similar to a Strowger dial, I think it IS a Strowger dial!

It is a little different Harry, Strowger has 11 finger holes and it has 10. 

[dsk]

I have heard that this dial was Strowger dials, but I have also heard that the 11'th hole on the Strowger dials not did give any 11 pulses, just the same as 0.

I have never seen a Strowger dial for real, and have not seen detailed pictures of the mechanism.

This Siemens telephone was reasonable to tune in hence of speed and make/break ratio. I have adjusted the break percentage from 69.4% to 62.45%  This is within 7% off for both 60 and 67% systems, and will be within the production specs for both systems for phones made as late as 1970.

dsk

[Jim Stettler]

I have heard that this dial was Strowger dials, but I have also heard that the 11'th hole on the Strowger dials not did give any 11 pulses, just the same as 0.

dsk

I think it is a strowger dial.
And on the 11 hole dials the 10 and 11th hole are strapped together
Jim S.

[HarrySmith]

The internals look like what I have seen in pictures of Strowger dials. I have never had one.

[.....]

Here are some pictures of my Strowger.

[dsk]

That is even a more complex dial.
I believe these were of a kind where you first dialed the number wanted, and then manually sent the ringing signal to the other party. A smart man that undertaker.

dsk

[rdelius]

I think the large dial Strowger systems were a 3 wire system.V (vertical, R (rotary) and G (ground) instead of Tip and Ring.Was the German system the same or was the telephone set modified for bridging like modern sets?

[dsk]

The ZBSA 11 was made for use on 2 wire systems, but  they were also compatible with a 3 wire system grounding one wire when dial was out of rest position.  This grounding while dialing function are not seen on diagrams of Siemens phones from 1936 and later.


e. g. the first anti sidetone version W28:
had this E terminal on the dial. The contacts named nsa is the contacts shorting the voice part of the circuit when the dial is out of rest position. The contacts marked nsi is the impulse contacts of the dial.
The German phones including modell 36 (1936) had the dial before the hook switch, and the hook switch had a mechanical device blocking the dial from been used in on hook position.  (Pretty strange from my point of wive.)


dsk

[RB]

Wow, those dials are bazar!
How long did it take to assemble one of those?

[dsk]

Yes and no!  The dials are huge, and it is not difficult if you compare to a Swiss watch of the same time. In that way I am more impressed by the extremely compact BTMC 7001 dial.
If we compare with modern rotary dial, the old ones are complicated, and even the way of solve the same problems involves just a few simple components. I'll have to look for a pretty new super-simple Siemens dial.


Edit:
Found a photo of a simple dial. Just as the first ones you have a finger wheel with a spring return, but then, a plastic part who contains a gear, the contact moving tabs for the rest and pulse contacts, all in one. a gear with a gyroscopic break regulator of the simplest possible solution, and 2 set of  contact springs.


dsk

[dsk]

Now I have picked up the missing bottom plate, and I also got the original tea strainer looking transmitter cup


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