On Tue, Nov 18, 2003 at 03:36:57PM -0500, Derrick 'dman' Hudson wrote: > On Mon, Nov 17, 2003 at 07:59:08PM -0500, lee wrote: > | Sorry to get off topic but I need to re-wire my DSL connection at home here > | and need to buy some phone wire and am curious if there is a good/better/best > | type of wire I should purchase..will be a direct run to my modem going about > | 100' or so from my box.. > > Typically phones use Cat 0 (or is Cat 1 the lowest?) cable. That > cable has 0 twists in it.
This is commonly known as "station wire", and is used a lot less these days in telco work primarily due to cross-talk problems on multiple line systems. > > 10BaseT (10Mbs) ethernet requires at least Cat 3, which has 3-5 twists > per yard (or something like that). This is frequently used for phone pre-wires. > 100BaseT (100Mbs) ethernet requires at least Cat 5, which has 3-5 > twists per foot (or something like that). > > Gigabit ethernet requires at least Cat 6 or 7, which has 3-5 twists > per inch. > > (all of these are "UTP" - Unshielded Twisted Pair - type cables) > > > Why are twists so important and why do the faster technologies need > more twists in the cable? As an electric signal varies along a pair > of wires, a magnetic field around the wires is created and then > collapses. This field will induce a current in another wire that > passes through the field. That induced current is "noise", because it > intereferes with the electric current (signal) that is intentially > being sent over that wire. Twisting the wires reduces the size of the > generated magnetic field, and also reduces the cable's ability to pick > up a signal from a nearby magnetic field. This is what causes the crosstalk between the pairs in station wire. > For voice-grade telephone, no twists are needed most of the time. For > better signalling and less noise, get more twists. Using Cat 0 or Cat > 3 should be fine, but the Cat 3 will cost more money. You *may* have > noise problems with Cat 0 which will hurt your ability to connect, > maintain a connection, and will limit transfer rates. Basically "more > is better" when it comes to twists, but also "more costs more". It's > up to you to find the desired return-on-investment for cable quality. I just use cat-5 for everything, there is not enough cost savings with cat-3 to justify having the extra boxes of wire. I don't use station wire for any runs more than a just a few feet. dt -- Dave Thayer | WARNING: Persons denying the existence of Denver, Colorado USA | robots may be robots themselves. [EMAIL PROTECTED] | -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
