Since the signal from a Campbell system is due to noise caused by the random nature of the de­tection process, it is reasonable to expect that reactor noise, could increase the size of the signal. This additional output is not an error, for it is shown on the following pages that it, too, is propor­tional to the reactor flux(except for some very low-frequency noises caused by mechanical disturban­ces; these very low-frequency noises are filtered out by the relatively high-frequency bandpass of the amplifier). The magnitude of the additional, flux-proportional signal, caused by reactor noise, is also very small due to low detection efficiency and the low frequency of the reactor noise coupled with the relatively high-frequency bandpass of the amplifier. The magnitude of additional signal caused by reactor noise is obtained in two ways.