Ethernet vs cross-over

I fully apologize that it' has been weeks since my last full update.

Due to some issue with work schedules and a family emergency I was unable to update on my normal weekly schedule. I'm doing my best to get back to that starting now.

Normally published on Friday night... you can expect your next update on 4/24/09

ok On to the juicy stuff.

I told you that Iw as going to explain what a CAT 5 ethernet cable is and how it differs from a cross-over cable.

First let me say I found an excellent resource here.

According to Wikipedia:

Category 5 cable, is a twisted pair (4 pairs) high signal integrity cable type often referred to as "Cat5". Many such cables are unshielded but some are shielded. Category 5 has been superseded by the Category 5e specification structured cabling for computer networks such as Ethernet, and is also used to carry many other signals such as basic voice services, token ring, and ATM (at up to 155 Mbit/s, over short distances).

The important part of this is the twisted pair part. The reasons the different pairs of wire are twisted, and each pair has it's own twist frequency, is to minimize "cross-talk" or signal transfer from one pair of wires to another. That's the basis for a whole article in and of itself, so we will just leave it at that. The important part of cross-talk is to remember that if you are stripping CAT-5 wire in order to punch it down to a block or jack, don't untwist the wires further than you have to in order to make the connections.

OK here is a diagram of a standard CAT-5 ethernet cable:

The cool thing is that EVERY CAT-5 calbe looks just like this. The outer sheaths vary according to the kind of use the cable will be put to, however the inner pairs remain the sames standardized in the IEEE standard on CAT-5.

whats that mean to you? you can look at any ethernet cable and expect to see a blue wire and a white wire with a blue stripe, a brown wire, and a white wire with a brown stripe, a green wire and a white wire with a green stripe, and last but not least, an orange wire and a white wire with an orange stripe.

Not only do the cables have a standard, they also fit together in a standard method.

Standard, Straight-Through Wiring (both ends are the same):

RJ45 Pin #	Wire Color (T568A)	Wire Diagram (T568A)	10Base-T Signal 100Base-TX Signal	1000Base-T Signal
1	White/Green		Transmit+	BI_DA+
2	Green		Transmit-	BI_DA-
3	White/Orange		Receive+	BI_DB+
4	Blue		Unused	BI_DC+
5	White/Blue		Unused	BI_DC-
6	Orange		Receive-	BI_DB-
7	White/Brown		Unused	BI_DD+
8	Brown		Unused	BI_DD-

Straight-Through Cable Pin Out for T568A

Straight throug, or standard ethernet cable, means that the wires are straight through from one end of the cable to the other. Both ends are the same if you hold them and look at them side by side.

Just be aware that if you are told you will need a crossover cable that you can not use a straight through cable in it's place, or vice verse.

this is jsut the difference between crossover and straight through calbes. anyone else have questions?

Links:

http://www.ertyu.org/steven_nikkel/ethernetcables.html

http://en.wikipedia.org/wiki/Cat_5