Abstract: An improved portable detection system incorporates a clock generator to produce a periodic signal that enables the user to properly pace his sweep and more readily identify targets in a first searching mode of operation. In the first mode, the detected signal is compared with an updated background developed from the previous sweeps, thus reducing the possibility of false alarms or missed targets. In a second pinpointing mode, background updating is discontinued and the developed background is used for target pinpointing. In this mode, a modified audio presentation is used which reduces hearing hazards associated with conventional variable tone presentations and enables easier target location.