I've hooked up a Mac G4 Cube and an iMac G3 in the same room with the Ethernet cables and APC line-surge protection that I plan to use, and the two computers share files just fine. Then I hook them together with a 300ft. 4pair phone cable, and.... nothing. What have I done wrong? Is 300ft. too far for an Ethernet signal to travel, or is the phone cable not up to the job.

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Yes, you?ve used phone cable, which is not up to the job. The distance isn?t the problem, although 300 ft. is the maximum distance. The problem is that phone cable doesn?t use twisted pairs. In a data environment, the cabling needs to be twisted so that the electrical signaling in the cable remains out of phase. With untwisted pair cabling (i.e. phone cable) the electrical signals have created magnetic coupling between the pairs inside the cable. This magnetic coupling or what we refer to in the data world as crosstalk is far greater than the actual data signal. If the noise is greater than the signal data could never pass. Twisted pair cable alleviates this problem. Stick with your Ethernet cable and your problem will disappear.

This was first published in April 2002

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