Hardway Jr Edward V, Holtman William H: Activity and respiration monitor. Cavitron Corporation, Sperber P, Pohl P H, December 16, 1975: US3926177 (107 worldwide citation)

A contactless activity and respiration monitor is described which includes a resilient, capacitive pad, which may be a mattress, or a pad used with a mattress, having a capacitor therein responsive to the activity or respiration of a body lying on it. Electronic capacitance sensing circuitry is disc ...