Abstract: In combination with a pulse transducer characterized by a source of light and a detector for light reflected from blood vessels of a living body, to provide heart signal consisting of a modulated dc signal voltage indicative of the pulse rate for the body, an artifact signal resulting from a reflection of light from the skin of the body, which includes both a constant dc signal component and a modulated dc signal component the amplitude of which is greater and the frequency of which is less than said heart signal, a signal attenuator circuit including an operational amplifier for canceling said artifact signal from the output signal of the pulse transducer.

Abstract: The condition sensor system comprises a condition detector which produces a pulse when a parameter of the monitored condition exceeds a desired threshold. A resettable condition counter counts each pulse. A resettable timer is preset to produce a particular time frame. The counter produces a condition signal when the accumulated number of pulses within the time frame is equal to or greater than a preset count. Control means responsive to the incoming pulses and to the condition signal produce control signals that control utilization devices. After a suitable delay, the last detected pulse simultaneously resets the pulse counter and the timer, and prepares them for sensing another condition occurrence within the time frame.The invention has particular utility in the process of detecting rocking motions of blind people. A controlled, audible, bio-feedback signal is provided which constitutes a warning to the blind person that he is rocking.