I have a very large room that has entrances at both ends. Both entrances get about the same amount of traffic but it is mostly pass-through traffic. One end needs to be motion sensored as flipping a switch may not always be practical.

What I want to do is have a regular switch at one end and a motion sensing switch at the other end. They will both control 3 lights that span the room. I know that they have to be 3 way switches for them to work but my dilemma is how do I make it so I can turn them on by hand at one end and then let the sensor turn them off? Or, vice versa, the sensor turns them on and then they are turned off at the other end by the regular switch.

My electrical configuration is not an issue as I am building to suit the project. Any ideas in this one?

Thanks for reading.

I would check out:
Wall Switch
Select Downloads, then Occupancy Sensor Product Guide.
Delay off from 30 seconds to 20 minutes. You could have 1 at each end, and override so you can sit and read a book without having to wave your arm to let it know you are still there.
Since in design stage, might as well put in dimmer, Nice at night, saves on electricity.

I have looked at those before but had my doubts on how they would work. Let's say that I install 2 of the occupancy sensors at opposite ends of the room on a 3 way switched circuit and leave them set to 15 minutes.
1. If I trigger sensor A, which turns on the light, and trigger sensor B while I am walking through the room - would it shut off the light?
2. If I manually turn on sensor A, which turns the light on - would triggering sensor B turn it off?

1) It will restart the 15 minutes.
2) Manual override will not allow 2nd detector to turn it off.
If you want to walking and have it turn light on, go to other and turns light off, Little difficult,
As sensor does not know which way you are going, or to stay.
If you had beam all over the room Like Mission Impossible, would be no problem, even if you were still, beam would be broke, and light would remain on. Might be an idea to use
Photobeam along path, then it would turn on, then turn off when leaving, 5 second delay or more would help if you wobbled off direct path.

OK. I see the error in my logic. I wasn't thinking of the sensor as an on-off switch. I thought that the first trigger would send an 'on' command and that the second sensor would send a command when it was triggered that would be interpreted as an 'off' command.

Thanks for the advice. The way that you worded it enabled me to understand the concept perfectly.

This is what you are talking about, correct?

http://www.kpsec.freeuk.com/animated/swpara.gif

The link you provided was like an OR Logic circuit. If input 1 or 2 is on(or high) then output will be on(high), It is like that, with a delay off on both.
If one was to turn on and the other to turn off, you would have a problem if one person walked in one end, and second person walked in other door, light would go off.
Photo beam(s) starting to sound better.

This link shows 3 way switching:
Howstuffworks "How Three-Way Switches Work"
If you want instant on when you walk in door, an down path, and turn off Immediately when leaving fully Automatic. I will get Part numbers for you.
You would still have three way switching, and maybe a dimmer to override the automatic for staying in room.