An improved biological signal detector which is extremely sensitive, yet resistant to the effects of high frequency noise. A multiplexed signal representation of a plurality biological signals is demultiplexed by a detector circuit comprising a plurality of switches each of which controls an individual storage network. A switch logic control circuit synchronizes the various switches to close during the time intervals corresponding to the pulse amplitudes representing the particular signal of interest. The amplitude of the alternating component of each of the biological signals is stored in one of the respective storage networks over a number of pulse time intervals. In the preferred embodiment, the storage networks of the detector each have a time constant which is purposely chosen to be substantially longer than the time interval of the pulses. The long time constant of the storage networks allows the detector circuit to track changes in amplitude which manifest themselves over a relatively large number of time intervals, but prevents the detection of high frequency noise signals which may be present during the sampling intervals.
Jonathan P. Jaeb;M.E. Converse