The cable is plugged on a Zyxel VES1724-56 DSLAM. It is a VDSL cable.



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    Commented Nov 22, 2016 at 15:53
  • Google has the manual that will tell you everything you need to know about this unit and what connects to it. Commented Nov 22, 2016 at 19:54

3 Answers 3


I can't find a good authoritative source, but as per your picture, we also use in our ADSL and VDSL DSLAMs/MSANs.

It is an RJ21 connector, sometimes also called an RJ21X connector.

This page has the more accurate picture I can find. That is how we often use them, pack to a patch panel to break out into RJ11 ports (for testing in the LAB) or back to krone blocks in a live PoP.

This page has a wiring guide.

  • 1
    Beautiful ! RJ21 is exactly what I was looking for. My cable also break out into RJ11 connectors.
    – pHeoz
    Commented Nov 23, 2016 at 13:48

The connector is a Centronics 50 like this:

enter image description here

You have to look for a cable for 25 pairs male with centronics / amphenol connector like this or this:


This is variously called an Amphenol, a Telco 50-way connector, and sometimes (rarely) a Centronics. In the kinds of places where you find DSLAMs like this unit -- communication service providers-- the term "Amphenol" is what I've heard most. Basically it is a very convenient form factor for aggregating connections. In this case, the DSLAM is going to be aggregating multiple connections from end user premises (houses, apartments etc) and so instead of plugging in dozens of individual lines they are aggregated into the Amphenol and connected.

Amphenol was the standard connector used in telcos for aggregating DS1s. At higher densities other connectors are used, such as coax for DS3. These days fiber is also used a lot, for even higher densities.

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