On 12/25/2010 02:51 PM, Joe Zeff wrote: > On 12/25/2010 12:32 PM, Mikkel wrote: >> If you look at the cable, you will see that the wires are twisted in >> pairs. White-orange with orange, white-blue with blue, etc. For >> noise cancellation, it is important that you use pairs for each data >> path. On a short cable, you can get away with out doing this, but it >> is not a good idea. Each pair also has a different twist ratio - >> twists/inch. This helps prevent them from interfering with each other. > > This is a tad off-topic, but I think some of you might find it > interesting. My apologies to those who don't. > > Several years ago, I was doing phone tech support for a company. One of > our clients was having trouble with a piece of equipment connected by a > run of Cat-5 through a pipe. Part of the trouble-shooting was making > sure there weren't any cabling issues, so the client brought out an > electrician. Not only weren't the colors on the cable standard, they > were different at each end! Our only guess was that there was a splice > down in the pipe because whoever'd run the cable had run out of one > batch and simply spliced on another. I told the electrician that he'd > have to do continuity tests from one end to the other to match up the > colors, and he asked me how to do it. I had him put the client on and > told him to get in an electrician who knew how to do his job. Yes, my > boss would have backed me up if there'd been a complaint because that's > part of what an electrician is supposed to know. You have that right. For that matter, depending on what part of the country it is, he may also know how to terminate the cables, and have access to a tester that will certify the installation. But I do not think this installation would have passed any way. I suspect that the splices would cause a problem. (You can see how far from the end the splices are with the proper test equipment.) But the thing you have to remember is that not all electricians have the same level of training. In a lot of cases, you get what you pay for. I know I was somewhat expensive as far as hourly rate was concerned, but tended to be a lot cheaper as far a the cost of the job went. But a lot of companies only look at the cost/hour, and go with the lowest price. Then you end up with electricians like the one you talked to. Oh yes - I was not the electrician that specialized in networking - he normally had a couple thousand dollars worth of network test equipment in his service truck. I just had the punch-down and crimping tools, and a CAT-5 terminate certification. I did not usually do fiber optics, network troubleshooting, or CAT-5 cable certification. I knew how to do it, but I normally only did it on bigger jobs, not as a service call. Mikkel -- Journeyman Inside Wireman Retired from IBEW local 494 Milwaukee, Wisconsin.
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