3-Way wired odd?

Not that I have seen everything, but I have not been able to find this

3-Way wired this way in any of the books I have. This 3-Way switch is being replaced, which is my interest in this.

Background: Keep in mind, I didn't set any of this up. This is how it has been working. There is a hallway to the garage from the family room. There is a 3-Way switch on the side of the door to the family room to control a light in the hallway. At the other end is a motion detector switch which has the switch position of on/off/autio. It is left in auto almost all the time. When you come in from the garage or upstairs from the basement, this hallway light comes on. Likewise, if you come from the family room and open the door, the light comes on. If you want the light in the hallway on before you open the door, you can click this normal 3-Way switch and it turns the light on in the hallway. After no motion, the light turns itself off.

I took the cover off for the 3-Way switch and it doesn't look like anything in the books I got. It has a black wire side wired to the copper screw connection. A white wire side wired to the brass screw. A red wire side wired to the brass screw. (This is the part I don't understand.) The brass screw from the red wire has a YELLOW WIRE JUMPERED TO THE COPPER SCREW THAT HAS THE BLACK WIRE SIDE WIRED. (Sorry for the caps, but I don't think you can bold text in a posting.)

Why is there a yellow wired jumpered between the brass and copper screws? Does this allow the switch to be toggled to turn the light on, so that the motion detector on the other switch can shut it off itself? Should it be wired this way? I'm replacing the 3-Way there with a new one, should I just wire the replacement 3-Way switch the same way?

I admit I don't often have a need to put the light on before I open the door from the family room, since the motion detector works fine for this, but I don't feel like I should just remove this 3-Way switch. Some people out of habit would just except it there to have something to click before going in the hall way if they wish.

Please be kind in your reply. I do have a call out to a pro for things I can't handle. I've been successful in replacing other switches and outlets in the home, and with the help of this newsgroup I have certainly gained a better understanding of things. Thanks!

From your description, the light functions in automatic mode, regardless of the position of the regular switch at the faimly room end of the hallway. The yellow jumper makes the circuit to the motion sensor switch always on - so the motion detector is always in control. The only exception is during a very brief period of time when you transfer the regular switch. That momentarily (a matter of milliseconds) interrupts the circuit to the motion sensor, which causes it to turn the light on the instant the interruption stops.

If you replace the motion sensor switch with a regular 3-way switch, you don't need and don't want the yellow jumper. When you install the new switch, assuming you have no idea of which wire goes where( because the new switch is a "regular"

3-way and the old one is motion sensing), here's a foolproof method to wire it correctly. Observe all safety precautions while doing this. With masking tape, label the wires A, B, and C. Make a diagram of the switch, labelling the terminal screws 1, 2 and 3 Omit the ground screw from the labels. There are only 3 ways you can wire this, keeping everything in order. Wire A can be connected to either 1, or 2 or 3. Keep the wires and the terminals in order and wire it with A starting at 1. If that doesn't work, rotate so that A starts at 2 (which necessitates moving B and C). If that doesn't work, rotate once more and it will. Possibilities: A-1 B-2 C-3 A-2 B-3 C-1 A-3 B-1 C-2