On Mon 25 Aug 2008 10:54:00a, Mark Lloyd told us...

On Mon, 25 Aug 2008 12:24:11 -0400, "TWayne"
wrote:

[snip]

More than likely, all you need are the green and red wires. The
black and yellow wires would be used for a second line if you had
one. In a normal residential system, they are not used, even
though they may be hooked to terminals as if they are.

A telco will NEVER use the yellow and black lines for a second line
with a normal RJ-11 installation. Those are for lights and grounds
in key systems, etc..


A lot of the materials I've seen (including wiring diagrams for
jacks) say yellow/black is for a second line. Also, if you have a
third pair, blue/white for a third line.

I don't know about key systems, but aren't the lights (that use
yellow/black) obsolete?

Not if you still have those type of phones. Many people still do.

You can still buy small key systems; quite a few places make them. I
know Mitel Inc. manufactures them for their North American market.