This circuit provides a digital output indicating the presence or absence of the infrared (IR) carrier signal. The incoming IR signal is sampled by a clock at a frequency which is about 4 times the carrier frequency. The high and low samples are tabulated in two counters in a race. When 8 high or 16 low samples are counted, the envelope status flip flop is set or reset, respectively, and both counters are reset. The output of the envelope status flip flop represents the envelope of the IR carrier signal.