Hi Richard
Thanks for the fax. Now I understand it.

The thing that worries me about the string and light systems is that it MAY be possible to get round the back of them and not hit the sensor, althought that comes down to alignment I suppose. We only need 2.5 metres fully protected anyway.

We need a key interlock on the power to the thing too don't we ? So anyone doing maintenance can lock the doors open.

I agree with Jay that we need some kind of override, but I am loath to let it override the limit stop switches. There in lies trouble.

Steve