Free book on German Field Telephone equipment

[Funksammler]

If you follow the link below you will be able to download my free e-book on field telephone equipment. It describes the various field telephones, exchanges, cable equipment etc. etc.

Previously this document was available via an earlier thread but the link to the document disappeared. Not to confuse things I thought it better to post this new link in a new thread.

The document now lives in my Dropbox account. Clicking the link leads you to a Dropbox page, you need to click the "Download" button in the top menu bar to start the download.

https://www.dropbox.com/s/ropwk8i433...20of%20WW2.pdf

regards,

Funksammler

[Satcong101]

Wow that's fantastic Funksammler a wonderful source of information thank you.

Is there a 'part 1' as it say's 'Part 2' in the title bar?

[Funksammler]

Wow that's fantastic Funksammler a wonderful source of information thank you.

Is there a 'part 1' as it say's 'Part 2' in the title bar?

Part I will be portable radio equipment, if I ever find the time to finish it!

regards,

Funksammler

[Val]

Nice, now search also works!

[fjs182]

Great Work! Thanks

[Funksammler]

New link after Dropbox disabled the old one due to security issues: https://www.dropbox.com/s/nons1x1uvw...20of%20WW2.pdf

regards,

Funksammler

[kabel]

This book has helped me a lot, but it has an error (found so far)
Book: https://www.dropbox.com/s/nons1x1uvw...20of%20WW2.pdf

At page 21 the "Table phone Tischfernsprecher 38" is stated to be something more than a magneto telephone, and I am pretty sure this was the intention when it was designed, but somewhere in the work to make the phone better the capacitor(s) C2 (and C3) was added, and it lost the possibility of proper work on a central battery line. (shorting C2 solves that)

I actually doubt that the automatic ring off in SB environment worked due to the high ringer resistance, but have to little knowledge about this system.

So if you want to use your OB38 (or OB39) at your regular telephone line short out C2 if it is in your phone(, like mine). (do not use the crank when connected to a regular phone line. You need the battery, and ofcourse you may not dial out since you have no dial.

Kabel

[Funksammler]

The Tischfernsprecher 38 still needs a microphone battery, it was never intended to work purely on a central battery but it can be connected to a ZB system. The capacitors C2 and C3 are there to keep the ZB voltage away from the speaker system, so they should not be shorted. The automatic ring off system is designed to work with Feldklappenschrank systems, the pulse is enough to make the indicator flap on the exchange fall, it was never intended to ring any bells. Obviously, the Tischfernsprecher 38 is not designed, and should not be used, on modern phone lines; for that you need an Amtsanschließer 33. Nowhere in the book is there any suggestion that it could; wrong use of equipment can hardly be attributed to an error in the book...


regards,

Funksammler

[kabel]

The Tischfernsprecher 38 still needs a microphone battery,

Yes it needs a battery

it was never intended to work purely on a central battery but it can be connected to a ZB system.

ZB is the German short for CB (Central battery) This was used on both manual and automatic systems,
without a dial the manual system would be whit it is intended for.
But it will not work on such system! On an automatic system a CB telephone will just be able to receive calls.

The capacitors C2 and C3 are there to keep the ZB voltage away from the speaker system, so they should not be shorted.

Partly right, the C2 blocks DC from induction coil, and this is preferable, but not used on some bunker telephones for ZB/OB. C3 protects the receiver from DC, but DC in this part of the circuit is unlikely, this C3 is also left out in the bunker telephones.

The automatic ring off system is designed to work with Feldklappenschrank systems, the pulse is enough to make the indicator flap on the exchange fall, it was never intended to ring any bells.

As I stated I have not enough knowledge about this system but on my kleiner klappenschrank it will not ring off unless I crank it

Obviously, the Tischfernsprecher 38 is not designed, and should not be used, on modern phone lines; for that you need an Amtsanschließer 33.

Of course it could not be designed for systems developed later, but the off hook registration is equal today, it requires formally a current of 18 milliamps, and will probably work at less, and that was in 1920, and that is today.

Nowhere in the book is there any suggestion that it could; wrong use of equipment can hardly be attributed to an error in the book...

The book states that it can be used at ZB systems. If You may get the dial tone, or may answer an incoming call on your POTS line, I was wrong, and you have my apologies.

regards,

Funksammler

I happen to have access to a working CB exchange designed before this phone, but made after WWii. I will do some more testing.

Kabel

[Funksammler]

I must admit, I did not try the TF38 Schulsszeicnen with the Feldklappenschrank, and looking at the schematic I can't quite figure out where the energy for the Schlusszeichen comes from. I think it needs a more complicated exchange like the earlier 10 line exchange or the Großer Feldklappenshrank. It calls from some more experimentation...

regards,

Funksammler

[kabel]

This went fast, and it would not seize the line unless I increased the load more than what the 1400 ohms ringer would do.
I tried a 1000 ohms resistor between W2 terminals, and then I got the dial tone.

To compare, The SB zusats uses a 300 ohms (dc resistance) coil for the SB signal,
and the
AMTSZUSATZ für den kleinen Klappenschrank zu 10 Ltg. uses one at 450 ohms.
The Amtsanschliesser has approx 380 ohms (measured)

I do not think the book is wrong in hence of what the idea was, but somewhere in the development back in the 30ies they changed the design.

Kabel

[kabel]

I must admit, I did not try the TF38 Schulsszeicnen with the Feldklappenschrank, and looking at the schematic I can't quite figure out where the energy for the Schlusszeichen comes from. I think it needs a more complicated exchange like the earlier 10 line exchange or the Großer Feldklappenshrank. It calls from some more experimentation...

regards,

Funksammler

Her will I absolutely agree, but still I wonder about the design in hence of the values.

regards,

Kabel

[kabel]

If you look at this bunker telephone circuit
you may follow the ZB circuit going trough the transformer (induction coil) this is blocked by C2 on the OB38.

I have read those pages many times, and did not find anything wrong before I got my phone, and tried it out.

I will not like to short out the C2, but I love to use my phones, and it had been funny to have an OB38 on the table beside my bed, and be able to answer calls.

I have used the Amtsanschliesser but it is better to use it with the field exchange.

The Amtsanschliesser is one of the most impressing instruments I relate to telecommunication, compact and able to solve so many problems!

Regards,

Kabel

[kabel]

The picture did not show up:


When I now has pointed out that the book not tells everything, I can not see how the writer should have seen this without testing it, and he has done a great job witch I am very thankful for.

It may be so simple that it was intended to be added something on the W2 terminals when used in ZB or/and OB systems.

This telephone is also known as OB38 and OB = LB (local battery)
A little notice in the article about this phone like: "Some users has reported problems using this phone as ZB (CB) phone. Adding e 600 ohms ringer on the W2 terminals is reported to solve the problem. (This are (not) confirmed.)"

Regards,

Kabel

[kabel]

This book has helped me a lot, but it has an error (found so far)
Book: https://www.dropbox.com/s/nons1x1uvw...20of%20WW2.pdf

At page 21 the "Table phone Tischfernsprecher 38" is stated to be something more than a magneto telephone, and I am pretty sure this was the intention when it was designed, but somewhere in the work to make the phone better the capacitor(s) C2 (and C3) was added, and it lost the possibility of proper work on a central battery line. (shorting C2 solves that)

I actually doubt that the automatic ring off in SB environment worked due to the high ringer resistance, but have to little knowledge about this system.

So if you want to use your OB38 (or OB39) at your regular telephone line short out C2 if it is in your phone(, like mine). (do not use the crank when connected to a regular phone line. You need the battery, and ofcourse you may not dial out since you have no dial.

Kabel

I have to admit to having been wrong here, my phone has the wrong ringer, the right one should not have 1400 ohms but 340 ohms according to measurements from an other owner of the OB38. With this low resistance, the phone will work as described in the book.

I also have to thank Funksammler for coming with arguments forcing me to dig deeper.

The 340 ohms could be the 2 coils of about 700 ohms in parallel, whil the OB39 has a 1400 ohms ringer. What I have written in the last posts will be valid for the OB39.

Regards,

Kabel