Author Topic: Ericsson DBK1001T  (Read 5472 times)

unbeldi

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Re: Ericsson DBK1001T
« Reply #15 on: August 20, 2015, 08:50:14 AM »
Very nice find. These are quite rare.

Here are my 2 cents:

I know this particular Phone as a knarretje (in Dutch, but the Swedish word knar seems to mean buzzer). It is a smaller version of the model 31.

It was meant to be an extention Phone, like for bedrooms, or as a normal unit for office environments where loud bells were not wanted.

It comes with a buzzer or without one.

The designation 1001 seems to be for a dialless version, so maybe this one was converted?

44 41 as an Ericsson date code would mean year and week number. (possible the other way around).

The is a page in the Swedish database here:

http://www.stsf.org/Schema/DBK/DBK1001.jpg with schematics.

It is also in the 1934 catologue om the Ericsson History website.

Both are pictured below.

How did you make the cross-reference to that catalog page with DE752 and DE3010. I looked at the very same page when browsing the catalog and didn't see a direct relation.

unbeldi

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Re: Ericsson DBK1001T
« Reply #16 on: August 20, 2015, 08:57:36 AM »
The phones works when the line is connected to terminals 1 and 3, and the buzzer works when the line is connected to 1 and 5.

That is indeed what the diagram tells us it should do.

The diagram also indicates that you can install a strap between 3 and 5 (EB) or connect an Extension Bell at those points.

unbeldi

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Re: Ericsson DBK1001T
« Reply #17 on: August 20, 2015, 09:17:47 AM »
It seems to me that the DBK 1001 replaced the CG552 from the same catalog, which was noted on the handwritten model page.

Offline dsk

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Re: Ericsson DBK1001T
« Reply #18 on: August 20, 2015, 04:22:06 PM »
You are probably right again. The metal plungers were later replaced with bakelite, at least on the more common telephones.

dsk

Offline LarryInMichigan

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Re: Ericsson DBK1001T
« Reply #19 on: August 25, 2015, 01:15:18 PM »
I just reassembled the phone.  The sound quality from the metal diaphragm transmitter is quite poor.

Here are a couple of blurry pictures showing this phone with two other related models, a Dutch PTT Ericsson Rijen phone and a British GPO 300 series.  The GPO phone dwarfs the DBK1001T.

Larry


Offline dsk

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Re: Ericsson DBK1001T
« Reply #20 on: August 25, 2015, 01:45:48 PM »
I don't know why the US transmitters was better designed than European? But they definitely were.

The DBK1001T transmitter needs to operate at an extremely low current and voltage so a LB transmitter may be the best replacement.

dsk
« Last Edit: August 25, 2015, 03:01:18 PM by dsk »

unbeldi

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Re: Ericsson DBK1001T
« Reply #21 on: August 25, 2015, 02:52:25 PM »
I don't know why the US transmitters was better designed than European? But they definitely was.

The DBK1001T transmitter needs to operate at an extremely low current and voltage so a LB transmitter may be the best replacement.

dsk

You mean a CB (common battery) transmitter would be better?

@Larry:  Are there any markings on the transmitter that might identify it for LB vs. CB operation?


Offline dsk

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Re: Ericsson DBK1001T
« Reply #22 on: August 25, 2015, 03:06:07 PM »
Local battery transmitters use 1.5-4.5 volts.  finer granulate is better until clogging up, it is a lot of parameter.
The circuit in this telephone has a current passing trough the balance winding, so not everything goes trough the transmitter.

I would just tested with different US capsules.

dsk

Offline LarryInMichigan

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Re: Ericsson DBK1001T
« Reply #23 on: August 25, 2015, 03:26:37 PM »
On the back of the transmitter is "RLA1401" and "200Ω".  The handset is designed in such a way that the shape and size of the transmitter capsule are very important.  The capsule fits exactly into a frame in the handset and the mouth piece fits tightly against the top of it.


Larry

unbeldi

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Re: Ericsson DBK1001T
« Reply #24 on: August 25, 2015, 03:56:04 PM »
The RLA 1401 is at the bottom of this page, equiv. RLA 1612, but the earlier description applies.

Indeed 200 Ω unit, seems pretty high.   This confirms it is at least a CB element.

Perhaps you should try to measure the current it draws on your line.
« Last Edit: August 25, 2015, 03:59:44 PM by unbeldi »

Offline LarryInMichigan

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Re: Ericsson DBK1001T
« Reply #25 on: August 25, 2015, 04:02:22 PM »
I connected a 390Ω resistor in parallel with the transmitter so that it doesn't continuously generate static, but the frequency response sounds like a metal diaphragm transmitter on 1920s candlestick.  I am a bit surprised that Ericsson was selling phones with transmitters like this in 1941.  I should be able to use the phone, but the person on the other end will wonder if I am speaking through a metal tube.

The phone is rather cute though.


Larry

Offline LarryInMichigan

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Re: Ericsson DBK1001T
« Reply #26 on: August 25, 2015, 04:16:52 PM »
I just tried using a T1 transmitter and it actually does seem to fit well enough in the handset to be usable despite the size and shape difference. 

Larry

unbeldi

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Re: Ericsson DBK1001T
« Reply #27 on: August 25, 2015, 04:24:34 PM »
The transmitter seems pretty large for a tiny phone like that.  T1 is about 7 mm smaller.
I guess the handset is full-size?

Offline dsk

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Re: Ericsson DBK1001T
« Reply #28 on: August 25, 2015, 04:46:05 PM »
You allready have the anti-sidetone circuit across the receiver. the current goes trough a 32ohms winding, splitting up in to the 200 ohms receiver, and the anti sidetone winding of 600 ohms.  The 200 ohms transmitter containes finer (smaller) granulates, it will be more sensitive, but clog or burn easier. The maximum current to the phone are described as low as 30 milliamps.
You loose 1/4 in the anti-sidetone winding. so the max in the transmitter should be: 22.5 milliamp!

Just like in Kellog's triad circuit (redbar?)

dsk

Offline LarryInMichigan

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Re: Ericsson DBK1001T
« Reply #29 on: August 25, 2015, 04:52:29 PM »
The handset is the standard size.

Larry
« Last Edit: August 25, 2015, 04:57:32 PM by LarryInMichigan »