Spectrum Sentinel Sound Detector Substation The Sentinel detects a preprogrammed audio alarm signature such as a scream, shout, or other type of duress situation and automatically places a call to the master station. Sentinel uses a Windows®-based software package to remotely program any of the substations' automatic day-night alarm thresholds, separate high and low frequency cutoff, and ambient noise gain. Individual stations can be programmed differently, based on ambient sound conditions. The easy-to-use Sentinel graphical interface transfers data instantaneously; thus, adjustments on the substations are effective immediately.