Abstract: An integrator for totalizing with respect to time an input signal representing a process variable being metered to provide a total reading for a given period. The integrator includes a drop-out circuit functioning to abruptly reduce to zero the signal fed to the totalizer when the input signal falls below a predetermined level where it no longer accurately reflects the variable. The input signal is applied to a duty-cycle converter that cyclically generates a rectangular wave whose ON period has a duration which is a function of the input signal, the higher the signal level, the shorter the OFF period in the cycle. Clock pulses at a constant frequency are normally supplied to a totalizer during the ON period. A drop-out counter functions to count the clock pulses during the OFF period, the number of pulses counted representing the duration of this period.