[nzlug] long wire: cat5 or phone?

[Andrew Errington]

On Mon, 28 May 2007 09:13, you wrote:
> Yuri,
>
> > The reason for keeping phone and ethernet on physically differently
> > shaped jacks is that I don't know what harm can come from connecting a
> > computer's ethernet port to an incoming phone line, or a fax machine
> > to an ethernet router. Also, the BT phonejack modules have the
> > capacitor thingy that makes phones work, and are telepermitted.
>
> You shouldn't be able to break anything if it is all wired correctly.
> Ethernet uses the first two pairs (1/2 and 3/6).  The phone should use
> the third pair (4/5).

Actually...

In T568A wiring (which is the standard I adopted), the first pair, or pair 
1, is Blue and Blue/White, and connects to pins 4 & 5.  The second pair, or 
pair 2, is Orange and Orange/White, and connects to 6 & 3.  Pair 3 is Green 
and Green/White on pins 2 & 1, and finally pair 4 is Brown and Brown/White 
on 8 & 7.  So, the phone uses the first pair.  10/100 ethernet uses pairs 2 
and 3.  Gigabit ethernet uses all four pairs.

Generally the 'punch-down' connectors on the back of the RJ45 sockets have 
colour coded stickers to say which wire goes where.  All you need to do is 
choose T568A or T568B and use the same colour code at both ends.  T568A and 
T568B are electrically identical, but the green and orange colours are 
swapped.

David is right- the first phone line coming in to any premises is usually 
on pair 1, the Blue pair.  If you 'reserve' this pair for phones and use 
only pairs 2 and 3 (Green and Orange) for Ethernet, then they won't cross.  
However, there are a plethora of adaptors and doodads which will plug in to 
an RJ45 socket so you really should be confident about what is at each end 
before you plug something in.

In my house I am using the Cat5e network cabling and patch panel to run the 
following services:

1) 10/100 Ethernet
2) Phone
3) Parallel port line extender (uses two pairs to extend the parallel 
printer port on my router in the comms room[1] to my printer in the study)
4) Serial communication to my anemometer in the back garden (I use pins 1-8 
on the RJ45 as pins 1-8 on a DB9 serial port connector.  Pin 9 on the DB9 
is ignored)
5) Dallas One-Wire bus to temperature sensors in the lounge and front 
garden, and to my water-meter counter sensor.
6) Video signal and dc power to the webcam at the back of the house (I use 
two video baluns, which use pair 1 for video, and I use one other pair to 
run 12Vdc to the camera)
7) 24Vac power to a solenoid valve which controls the irrigation on the 
vege patch.

I have two 12-port patch panels in the comms room[1].  19 of these 24 
positions are wired up, and 5 are not yet used (but I have an idea of where 
I want to put sockets for these).

The cool thing about having Cat5e everywhere is that you don't need to run 
new wires every time you think of something else you want to hook up.  If 
you put two or three RJ45 sockets at strategic places then you are well 
provisioned for the future.  Also, Cat5e can be thought of simply as '8 
wires from here to there' and you can use some or all of them in any way 
you see fit.  The Dick Smith part XH4248 lets you run ethernet and phone on 
one cable (leaving one pair left over), but there are adaptors to allow you 
to run two ethernet services on one cable (2 pairs each), and I have made 
my own for video + power (but I have seen them for sale), and it's trivial 
to do serial.

Crawling under the house for however many hours (whilst suffering the 
bruises and scrapes from all those pieces of broken tile) was totally worth 
it!

A

[1] The hot-water/linen cupboard.