Finding a good trade-off among the probability of detection (POD), the false alarm rate (FAR) and the reliability of detectors is a very important task in physical security system design. Existing solutions try to achieve this aim either by using the most advanced technologies or by combining basic sensors in logical OR/AND relations. However, these approaches are either not cost-effective or they do not allow for the necessary flexibility to obtain the right balance. In this paper I propose a majority voting scheme for multiple technology detectors which I evaluate using stochastic modelling techniques. This solution has the major advantages that it permits good overall dependability while using low-cost detectors, and also enables a precise fine tuning of POD and FAR parameters. To the best of my knowledge, no similar system has been studied in depth in the research literature. I provide a set of results which clearly show the advantages of the proposed approach.