ISDN adapter killed when connecting it to GS1100-24.

josef Posts: 2  Freshman Member
edited August 2022 in Switch
A very strange thing happened.
From my telekom provider I received a new router (VOIP) an along with it an ISDN adapter to keep my ISDN telephone exchange system going. The router works fine. Installing the ISDN adapter I first configured it connecting directly to the router with a LAN-Ethernet cable and testing with an ISDN telephone. This worked. Then I went to the basement where the ISDN telephone exchange system is located. To make a connection to the router I connected the ISDN adapter to the GS1100-24 switch with the result that the adapter was killed immediately. Very strange!
Does anybody have an idea why this could happen? 
Are there electrical specifications for ethernet which possibly are not met by all devices?
I have no idea what happened but it would be useful to know  - I cannot afford to kill more of these adapters.


All Replies

  • Mijzelf
    Mijzelf Posts: 2,607  Guru Member
    First Anniversary 10 Comments Friend Collector First Answer
    edited April 2019
    Was the adapter already connected to the telephone exchange when you connected to the switch? Is the exchange earthed? Is the switch earthed?
    The only reason I can think of is that an electric potential difference between the exchange and the switch killed your router.
    Are there electrical specifications for ethernet which possibly are not met by all devices?
    No, except for POE switches. Which a GS1100 24 isn't AFAIK.

    /Edit: Or did you connect it the wrong way? Both ISDN and Ethernet use RJ45 outlets, but electrically they are completely different.

  • josef
    josef Posts: 2  Freshman Member
    Thank for your answer.
    I did not get that far to connect the adapter to the telephone exchange. I was still working with the ISDN telephone. 
    To be precise: First I connected the LAN cable from the GS1100-24 to the adapter. Next I connected the cable to the ISDN telephone to the adapter - and no, I did not confuse them, the LAN cable is yellow, the outlet in the adapter also. And then I connected the adapter to power.
    The status LED did not go on, and never again did it. 
    Earth: The adapter is a little box, and power (12V) comes from an external power source you plug into any 220V-outlet. The power plug has no earth. The ISDN telephone cable (S0-bus) in this case has also no earth. The only earth there is is the one from the LAN cable to GS1100-24.