Abstract: A method and apparatus for validating a moving coin by detecting an oscillating signal generated in coils connected in a tuned oscillating circuit. A property of the signal which varies linearly with coin displacement in one direction for a first period and varies linearly in an opposite direction with coin displacement for a second period is measured. From measurements made during the first and second periods a signal characteristic of the coin, and substantially independent of the coin's velocity is derived. The coin is validated by comparing this signal with stored reference values.