Scantronic 9800?

I wish to decorate my dining room which includes re wallpapering. I have a motion detector in the corner on top of the original wallpaper. I would like to omit this area whilst i do the decorating. Omit is allowed acording to the paperwork that the fitting engineer left with me. I have followed the instructions in the manual which states to enter my 4 didgit code then press omit then the number of the zone that i want to omit. Unfortunatly it is not omiting that zone and when i go to remove the detector from the wallpaper in the corner the alarm sounds. I would be happy to turn off the whole system if that is what is needed and then to turn it back on when i have completed the redecorations. Many thanks