On Monday, October 1, 2012 2:44:30 PM UTC-4, Dave Platt wrote:
I have to install an Internet connection at a location somewhat removed from the origination point. The building is very large, spread out, and difficult to run wire through. Presently there already is a connection terminated in an Rj45 at a point that is only used for one week out of every year. All other times there is nothing plugged into this jack but the connection remains active. In order to make the connection to the new location about 100 feet away can I tap off the existing jack and "daisy chain" the wire to the new location and then terminate that wire in a second R45? I now this is not common practice but if only one computer is using the line at any particular time would this work? It would probably work OK when you connect something to the jack at the end of the new run of wire. It may very well *not* work, for devices plugged into the existing jack, during that one week per year. The problem is that your new run of wire will create an "un-terminated stub" in the Ethernet transmission line. This is a no-no - signals travelling down the wire (from the middle jack to the unused new end jack) will arrive at the end jack, and will "see" an abrupt change in the characteristic impedance of the line (jumping up from 100 ohms or so in the twisted pair, to a very high impedance at the jack). The signals will be reflected by this impedance discontinuity, and travel back along the wires towards the existing (middle) jack. When they arrive there, they will mix with (and interfere with) the signals from the other end of the line, and it's very likely that the computed plugged into this jack will see a completely garbled packet as a result and will discard it. This is essentially the same problem which can create "ghosts" in an analog TV system, if you have an extra length of coax daisy-chained from a coax port. There are several ways to deal with this problem effectively. The one I'd recommend (inexpensive, easy, and it should comply with all of the standards and work fine): convert the existing outlet plate from one RJ-45, to two RJ-45 jacks. Run the "tap" line to the new location to the second RJ-45 on the new jack... do *not* hard-wire it into the existing line or jack! When you want to use the original location, plug the computer into RJ-45 #1 (the one which goes to your central location). When you're not using this location, and want to use the new location, simply plug a short Ethernet jumper cable into the two RJ-45 jacks. This approach can be extended to allow you to use both locations, at low expense. Simply buy an inexpensive 10/100 switch (4- or 5-port type) and place it at the existing location. Connect its upstream port to jack #1. Connect jack #2 to one of its downstream ports. When you want to use a computer at this location, simply connect it to one of the other downstream ports on the switch... no need to disconnect your new location. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!

Thanks for all the great ideas guys. I really appreciate them. Lenny