Abstract: A system is shown for detecting the movements of a patient confined to a bed so as to determine if there is the likihood that the patient is trying to leave the bed. A sensor is arranged to be placed under the mattress of a bed next to the frame and is totally sealed from the intrusion of contaminants so that it is not necessary to discard the sensor after a patient is discharged. The sensor utilizes ribbon switches sandwiched in assembly between stiff plexiglas plates. The assembly is sealed in a bag that holds the parts in assembly while permitting relative movement in all directions. The alarm system is arranged so that if the sensor detects undesired patient movement, the regular nurses' call light system is deactivated and an alarm distinguishable therefrom is superimposed on the nurses' call light alarm. In addition, an alarm audible to the patient encourages the patient to return to the desired position on the bed.