Uses refined noise-reducing hardware and a unique patented software algorithm. Instead of relying on a voltage threshold to determine a pulse, it analyzes a digitized signal at a rate of 120 times per second, and compares it to previous pulse data. These pulses are constantly stored and updated, and used as dynamic templates to determine the validity or invalidity for newly-encountered pulsatile signals. Patented Serial Autocorrelation (SAC) technology provides reliable monitoring.