Optional Universal Pattress for use with the HSA/IO, HSA/PE, HSA/HE and the new HSA/CO Interconnectable Carbon Monoxide detector. This Pattress is only necessary when the installer has limited or no access to the back of the detectors. Usually a cable is delivered down through the ceiling to supply the detectors. If this is not possible, maybe due to a concrete partition between floors in an apartment for example, a 'Universal Pattress' can resolve the problem.