ISDN NTBA

Hello everyone

ISDN was switched off, but I still use ISDN devicesā€¦ partly for #nerd purposes - so itā€™s not a matter of sense or nonsense šŸ˜ šŸ˜‰

There is an S0 interface on the Fritzbox 7590, to which I connected an old Swisscom ISDN NTBAā€¦ But it has given up the ghostā€¦

Since I canā€™t connect the devices directly to the FB (humming soundā€¦, Iā€™ve already made numerous attempts with termination boxes and resistors)

Are there still sources to purchase functional Swisscom NTBAs? Theyā€™re actually EOL, butā€¦ I still need one šŸ˜‰

Ev. at Swisscom itself? Or were all those returned scrapped?

Unfortunately I couldnā€™t find anything onlineā€¦

Thank you very much and have a nice Sunday

Greeting

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@Veittammo28 Most likely on Ricardo or Tutti

I have just dismantled various ISDN equipment for a customer, unfortunately already in the scrapyard

If I happen to get my hands on something like that again, Iā€™ll get in touch with you if I think of it and find this forum post

Edit: E.g. This: [https://www.tutti.ch/de/vi/basel/grossbasel/computer-zubehoer/components-zubehoer/t-net-box-isdn-ntba/62120528] (https://www.tutti.ch/de/vi/basel/grossbasel/computer-zubehoer/components-zubehoer/t-net-box-isdn-ntba/62120528) But not Swisscom, but I think Telekom (I had no idea about ISDN, I was still a toddler when it was used šŸ˜‚)

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@Veittammo28 You actually donā€™t need NTBA because the S0 voltage comes from the FB.

I think your FB has a defect. With an S0 splitter I can connect up to 5 devices.

The Swisscom NTBAā€™s always had 2 x analog interfaces.

The Telekom NTā€™s only 2x S0 interfaces.

The longer ISDN goes, the more it will die out, even though it was a very robust technology.

All EWSD have been shut down and dismantled for years.

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A hum is an indication of ground loops.

Before you replace the frit, try using the power supply of the Fritzbox and the telephone on the same power strip. If necessary, turn the two-pin Euro plug of a device (Fritzbox or telephone) by 180ā°. Should have helped too.

ISDN is also a digital bus. Because the hum is generated in the telephone and not in the frit. OK. The cause could still be the Fritzbox. Especially if all connected devices show the same phenomenon. As I understand you, you have several. Just donā€™t start the experiment with full expansion.

šŸ˜‰

But it remains a vague assumption on my part.

Ƅs Greetings

Android

šŸ‘½

Edit: Typo patched during full expansion.

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Thank you very much for your adviceā€¦

After a lot of rumbling around, without NTBA, but a phone directly on the S0 (which buzzed in every constellationā€¦ With/without distributorā€¦ Connected to socket, resistors on/offā€¦ Frit to UPS, and other sockets in all Iā€™ve now noticed somethingā€¦

When I touch with my (grounded finger) the contact that switches the resistor on and off, the hum goes awayā€¦

I find something strangeā€¦ There seems to be something wrong with the grounding, is this a common occurrence? Or what could it be? Otherwise I just ā€œearthā€ the whole thingā€¦ problem solved šŸ˜ But definitely not ā€œstate of the artā€

LG

IMG_0972.jpg

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  • user109 has responded to this post.

    @user109 wrote:

    @Veittammo28 if the earth is coupled to the PE, a hum loop can occur.

    Actually the resistance is between a1 and b1; a2 and b2 connected and not to earth (shielding).

    You may need to explain what you mean by PE. And in the picture from @Veittammo28, the orange cable has no shieldā€¦

    šŸ˜‰

    LG

    šŸ‘½

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    @Herby wrote:

    @andiroid

    Correct.
    and I think whoever did this installation back then probably didnā€™t read or understand ā€œthe manualā€ for ISDN installation; - )

    What exactly!? šŸ˜‰ You have identified the problem, should @Veittammo28 now read the ISDN installation manual?

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    @user109 wrote:

    @andiroid maybe somewhere else, the 50Hz has to be coupled onto the line from somewhere.

    ISDN would simply have to eliminate the 50Hz network frequency? The frequencies of 300-3400Hz are used and 50Hz hum should not be disturbing. But yes: If @Veittammo28 cannot temporarily connect the devices directly to the Fritzbox (?) then I see few options for analysis with our šŸ”®.

    I am a trained electronics engineer and not a Stomer. Could the problem also have its origins in the 230V installation? šŸ¤·ā€

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