Abstract: A coin validator is arranged to sample the outputs of electromagnetic sensors in order to derive measurements for use in testing coins. Frequency measurements are made by counting a predetermined number of oscillator cycles, terminating the sample period in response to this count being reached, and taking into account the duration of the sampling period and the number of cycles of the oscillator during the sampling period, including any cycles which may have occurred following the predetermined number. The predetermined number is altered in order to change the sampling period.

Abstract: A control circuit of a money-handling unit receives an input from a coin sensor, and detects whether liquid is present by detecting the occurrence of a false signal caused by liquid shorting the output of the sensor. Two different thresholds of conductivity can be used to detect whether liquid is present and to distinguish between high conductivity liquids and low conductivity liquids. The control circuit carries out different courses of action to respond to the liquid depending on the conductivity. Either a temporary or permanent shut down is selected.

Abstract: Apparatus for validating items of value is described. The apparatus includes a measurement circuit including an inductor, the complex impedance of which varies in accordance with the interaction between a test item of value and a magnetic field within which the inductor is located. Circuitry is provided for extracting first and second periodic signals from the measurement circuit, and a circuit is provided for timing the interval between corresponding portions of the first and second periodic signals. A processing element then determines the value of a parameter related to at least one of the real and imaginary parts of said complex impedance, as a measure of the validity of said test item, from the outputs of the timing circuit.