If you were to add a second line to your house, the installer would probably check and see if you were going to run the second line to every room or just to one of the rooms (like a computer room). I've seen installers use the yellow & black wires to run that second line in, instead of running a separate, new line. They just have to make sure the wall jack is wired properly.
I hope this helps you some. Happy Holidays!
Jim D/Heathsville, VA
The function of wires in communication cables depends on the utility service.
For example, if your "pots" line has been upgraded to a digital service such as DSL, the wires may be utilized differently. Anybody know this, and any problems using the black/yellow pair as described above?
Years ago, I worked on "four-wire" service communication lines that our company leased from the phone company, to enable data and voice communications from one facility/city to another. A pair of wires (red/green) was used for the Transmit signal; the other pair (black/yellow) for Receive.
Computer LAN (twisted-pair type) cable also has several pairs. If technology hasn't changed, there are four pairs, one for transmit, one for receive, etc..
[This message has been edited by gs99 (edited December 27, 2002).]
That sounds like an old Telephone Circuit Protector.
It is or WAS the telephone companies.
I don't know the teleco's policies are on this, but it should be removed.
And a Demarc should have been installed. That is the point where the Teleco lines end and your wires start.
Also called an NIC (network interface connection) or SNI (system network interface).
There are several different styles. But this is typical. They have a part where the teleco make connections and a customer side with a test jack.
When you unplug the jumper it disconnects the house wiring. Then you can plug is a telephone.
If it works OK there then the teleco lines are OK and the problem is inside.
If you don't have one of these then get them back and have them install one and remove the old protector.