OMRON BLOOD PRESSURE MONITOR M3, is a fully automatic upper arm blood pressure monitor, operating on the oscillometric principle. It measures your blood pressure and pulse rate simply and quickly. For comfortable controlled inflation without the need of pressure pre-setting or re-inflation the device uses its advanced technology. If the cuff was wrapped too loosely, it may cause unreliable values. If the wrapping of cuff is too loose, the cuff wrap guide lamp does not light. Otherwise lights in green. This is the function which is used as an aid in determining if the cuff is wrapped snugly enough