In normal operation, instrument gathers the pulses from the detector, measures their height, counts them and stores them according to their height, and then calculates the correct rem or rad. Every second it goes through this routine. The 3 standard time constants use an averaging algorithm that changes the time constant depending on the count rate. There are 2 lookup tables foe the average, one for slow and one for fast. Within each table, the TC varies as the dose-rate but the slower TC has all of the values slower than the fast TC table.