Abstract: A centralized system for simultaneously monitoring a plurality of predetermined remote areas and selectively indicating an unauthorized intrusion into any of the areas. A preamplifier is placed in each of the areas for amplifying the electrical signals from each of a set of microphones in that area and the amplified signal is coupled to a central monitoring and alarm station. The central station may provide a sound level indicating lamp for each area, an alarm lamp to indicate when the sound in each area exceeds a predetermined background or threshold level, and a system for simultaneously listening to the actual sound in all of the remote areas or selectively listening to the sound in any one of the areas.