An experimental system has been constructed which simulates the detection stage of a receiver. With the application of periodic bursts of sine- wave plus Gaussian noise at the input, the output of this system is a non stationary random process. The addition of noise to the signal suppresses the mean at the output for the half-wave linear detector. However, the mean is unchanged for the half-wave square-law detector. The non-stationary variance is seen to vary between two values which can be easily measured. Output signal-to- noise ratio is greater for the half-wave square-law device than for the half- wave linear device. Addition of a clipper to the half-wave linear device decreases the signal-to-noise ratio. Detection characteristics of the half-wave linear and half-wave square-law devices are found to be equivalent and the clipper degrades the detection characteristic.