I install hundreds of these alarms every year two lots of 3cores is the norm but not idea, it is possible to terminate three lots of 3 cores but it is tricky and I would not like to do it on a regular basis would much rather use a radio link if possible and take power from somewhere elseAs with previous posters I have the same issues with the inadequacy of the terminal box.By the way, I never connect them up as shown in the photo as I would end up tearing my hair out. I terminate before mounting the the base. Far easier.