The arrival of a coin in a coin checking apparatus is detected by arranging for the coin to hit a member (16). The vibration caused by the impact causes a piezoelectric element (36,36a) to give a transient output signal which is used to switch on electronic circuitry of the coin checking apparatus. The circuitry is normally switched off and thus over a period of time the average power consumption of the coin checking apparatus is low so that it can be satisfactorily run from a battery.
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