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Posted

hi guys, need some help with this.

i have a diagram of how to build this cable myself, but am stuck & confused where it says one wire to be connected in N/C.

need your help...

am gonna try attach the diagrampost-86435-0-83073500-1341858328_thumb.j


Posted

i have a diagram of how to build this cable myself, but am stuck & confused where it says one wire to be connected in N/C.

From what I can tell is that pin 5 on 6P6C (RJ12) needs to connect to any pin on 8P8C (RJ45) that isn't being used (4, 5, 8).

The N/C means that particular pin does not make a connection to whatever it plugs into. Since it is actually laid out in the diagram that it connects to pin 5 on the other side makes me think it might be used for grounding?

Anyways, this type of cable seems to be fairly inexpensive to buy.

Posted

N/C is the conventional name for Not Connected.

In this case it means that the RJ45 (that has 8 contacts) is used on a 6 wire cable of which one (the one connected to the Pin #5 on the RJ12) is cut SHORTER than the others and is NOT connected to ANY receptacle on the RJ45 side )or you can use a 5 wire cable, if you find one).

The schematics is evidently drawn by one of those nice guys that like to make things more complex than actually needed :ph34r:.

Usually it is "etiquette" to NEVER change the pin order on either side of a cable schematics.

Here are a couple examples of more "clear" schematics:

http://buzzdavidson.com/?p=24

http://ltxfaq.custhelp.com/app/answers/detail/a_id/328/~/cable-to-connect-a-dec-vt-terminal's-mmj-to-a-lantronix-rj45-serial-port

@Tripredacus, a wire marked N/C must NOT be connected to any pin/receptacle.

jaclaz

Posted

@Tripredacus, a wire marked N/C must NOT be connected to any pin/receptacle.

Ok I didn't know about "cutting the wire shorter" before. I suppose it depends entirely on whether or not the thing you are plugging into is also designed to not have a connection at that point as well. I had a certain picture in my head when typing that (ie USB connector block) which has the N/C pin physically removed.

Posted

Ok I didn't know about "cutting the wire shorter" before. I suppose it depends entirely on whether or not the thing you are plugging into is also designed to not have a connection at that point as well. I had a certain picture in my head when typing that (ie USB connector block) which has the N/C pin physically removed.

Yep :), same happens on RJ connectors, if you remove the "pin", since it is the pin itself that perforates the wire insulation.

Though it is usually quite difficult to remove a single "pin" from a RJ connector.

Point is/was that "better be safe than sorry" unless you know that *nothing* is connected to the pin #5 of the RJ12 receptacle, and besides there is no data to know if the "N/C" wire on the RJ45 receptacle would go on which among pins #4, #5 and #8 (you should remove all three of them, but usually, if on the RJ45 socket there are all 8 contacts, the ones that find the "hole" where the "pin" shoud be won't "like it" much and will tend to bend/stuck the connector :ph34r: ), cutting the cable shorter on the RJ45 side is the faster and safer way.

There is also another (remote) possibility, that on the RJ12 side the pin #5 is connected to a ground of some kind, in which case having a 6 wire cable with one wire connected to pin 5 on the RJ12 side and cut 2 or 3 millimeters shorter on the RJ45 side would provide a form of "shielding".

jaclaz

  • 3 weeks later...
Posted

i made the cable and it works, so the most important thing is to connect the pin 6 to the pin 8 diagram, the additional 3 wires in the pin8 i still them as space holders.

n/c means that the pin 8 does not make contact to the device or not connected

Thanks guys

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