The ClampOn DSP Well Collision Detector is a real time ultrasonic monitoring system for detection of a drill bit in the proximity of existing wells. The system provides real time data during drilling and thus supplements collision risk analyses and positioning data. The monitoring system lends from ClampOn's well-proven series of ultrasound sensors for sand monitoring, PIG detection, and leak detection. The working principle of the Well Collision Detector is discussed briefly. An application example from a drilling operation is shown to illustrate the utility of the system.