I would like to wire one jack for two lines. Here is the setup of the
> wires after opening the jack.
> The red screw terminal has two blue and 1 orange wires connected to
> it. The green screw terminal has 2 white/blue and 1 white/orange wire
> connected to it. I'm just curious as to why there are 3 wires
> connected per terminal.
I think you will find that your house was not wired "home run" to each jack. In other words, one pair goes back to the demarc block and the two other pairs go to other jacks in the house.
The yellow an black screw terminals are not connected to any
> wires. Now what should I do to be able to access a second line?
> [TELECOM Digest Editor's Note: Red/green is traditionally one pair;
> and yellow/black is traditionally the second pair. You want to use
> the unused yellow/black screw terminals for your second line. Can
> you tell us more about the _type of phone instrument_ currently in
> use on your (I presume) working single line? With no other knowledge
> it is difficult to answer your question; was this/is this part of
> a business phone arrangment? Does the pair which is 'wired' at
> present go to a working instrument? PAT]
The colors don't really matter other than for keeping track of what's going on. You need to start at the demarc and select an unused pair for the second line. When you get to the phone jack, you need to know if your phone is a single line or dual line phone. If its a dual line phone, then Pat's advice is correct. Wire line 1 to the inner pair of the jack (red/green on some jacks) and wire line 2 to the outer pair (yellow/black).
If the phone is a single line phone and you want it to access Line 2, you will need to wire Line 2 to the inner pair.