Help With Physical Layer

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Asterisk Users 7 Comments

Hello users,

I have a Digium Te235 and asterisk 13 which have worked well with 1
carrier but we have failed to add a 2nd carrier. The second telco brings their E1 line over finer, terminated in a RAD modem and they give me ethernet to the E1 card. It’s the first time i am having install such a solution, which ideally would be not a big problem.

However, The physical layer has failed to come up! I have tried the same setup in an Alcatel OmniOCX and it works well. I can confirm that the port is also well configured because when I interchange the cables (with the exiting cable from the other telco), the alarm clears emmediately for the
1st telco and becomes RED for the 2nd telco. A loop also clears the alarm on both ports.

The telco has told me to make sure that Line Impedance is 120 ohms but There’s no where to set that and when I was reading, I was told that E1 is already 120 ohms so no need to change anything.

Has anyone here experienced this? What other things can I try?

Thank you!

Regards, Tim

7 thoughts on - Help With Physical Layer

  • Dear David,

    I am sorry, I can give the answer right now as the box is at a remote location where I don’t have access right now. However, I think the card is ok and al the spans are working. Yesterday I had asked the telco to bring a new RAD modem and I also took there another dell optiplex 3010 desktop with another TE235 card in it but same results! I can confirm that the cards are ok!

  • Hi Dale,

    Yes, I tried a cross-over cable, I also tried terminated a new E1- cable with only PINS 1-2 and 4-5 but still no luck. Everything I tried, I would replicate with the other telco’s setup and results would be positive.

    I have a feeling this new telco brought a new model of a RAD modem that somehow doesn’t work with our cards but am struggling to find the technical reasons (and possible fixes) to support that hypothesis.

  • The new Digium cards have no jumpers anymore and I don’t think they support coaxial cables. The only changes we can make on the digium cards is to switch between E1/T1 modes and that’s done when loading it in the kernel using modprobe.

    I would doubt it’s the pinout but it’s possible. I have tried several cables (cross-over, straight-through, E1) and both didn’t work but surprisingly, they do on the other RAD modem that comes to the same PBX.

    Thanks for the pointers.

    I am going to keep trying several things and if I get a break through, I’ll definitely share the results.

    For no, any more help is welcome.

    thanks!