A apparatus configured to detect the presence of one or more unknown signals in the presence of noise and/or interference. The apparatus includes an input configured to receive an input data from a sensor, an integrator configured to integrate the power of the input data over a period of time, and a comparator configured to compare the integrated power to a threshold to determine if the input data contains at least one signal, or if the input data contains noise only. The apparatus may further include a mean estimator configured to estimate the mean of the power integrated input data over a period of time, a variance estimator configured to estimate the variance of the power integrated input data over a period of time, and a threshold calculator configured to calculate the threshold value based on the estimated mean or estimate mean and estimated variance.