Cisco FXS Port - RJ11 to RJ45

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Oct 1st, 2010
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I have a VIC3-2FXS/DID in Switerzland and my customer has asked for it to be connected to a fax machine through Strucuted cabling and they would like to know what type of cables they required.

They want RJ11 (FXS Port) to RJ45 (Patch Panel) then RJ45 (Patch Panel) to RJ11(Fax Machine).

Could someone explain the pins out of the cables, as it is going to be two RJ11 to RJ45 cables do they need to rollover?

Thanks for any help.

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Steven Holl Mon, 10/04/2010 - 09:10
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All cabling on Cisco voice cards is straight through from the port to the device. RJ11 has 2 pins, for tip and ring.  That's blue and white/blue. RJ45 has 8 pins, but if you want to stick with the 568B wiring standard on the RJ45 jacks,you would use this.

Blue: RJ11(pin1)----RJ45(pin 4)--------(pin4)RJ45-----(pin 1)RJ11

White/Blue: RJ11(pin2)----RJ45(pin 5)--------(pin 5)RJ45-----(pin 2)RJ11

If you actually have RJ14 jacks (4 pins), its pins 2 and 3 (the middle pins) which are used.  If it is RJ25, it's still the middle pins, which would be 3 and 4.


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