Device and method for the sensing of money items

1. An apparatus comprising:

a money item sensor comprising a resonant electrical oscillator circuit operable at a plurality of different oscillating frequencies to sense at least one property of a money item;

wherein the resonant electrical oscillator circuit is configured to trigger one or more switches to change an oscillating frequency by switching one or more capacitive components out of the resonant electrical oscillator circuit synchronously with a beginning of a new half-cycle of the resonant electrical oscillator circuit, wherein when switched out of the resonant electrical oscillator circuit the one or more capacitive components store electrical energy from the resonant electrical oscillator circuit; and

wherein the resonant electrical oscillator circuit is configured to trigger said one or more switches to further change the oscillating frequency by switching said one or more capacitive components back into the resonant electrical oscillator circuit synchronously with a beginning of a further new half-cycle of the resonant electrical oscillator circuit, wherein upon said one or more capacitive components being switched back into the resonant electrical oscillator circuit to adopt a particular configuration of the resonant electrical oscillator circuit an amplitude of the oscillating frequency matches an amplitude of the oscillating frequency when the resonant electrical oscillator circuit was previously in the particular configuration.

2. The apparatus according to claim 1 , wherein the resonant electrical oscillator circuit comprises an LC resonant circuit.

3. The apparatus according to claim 1 , further comprising:

a controller configured to measure fluctuations in the oscillating frequency of the resonant electrical oscillator circuit caused by a money item in a magnetic field generated by the resonant electrical oscillator circuit to determine the at least one property of the money item.

4. The apparatus according to claim 1 , further comprising a controller configured to:

measure a first fluctuation in the oscillating frequency of the resonant electrical oscillator circuit at a first base frequency of the resonant electrical oscillator circuit to determine a first property of a money item; and

measure a second fluctuation in the oscillating frequency of the resonant electrical oscillator circuit at a second base frequency of the resonant electrical oscillator circuit to determine a second property of the money item following a change in a base oscillating frequency.

5. The apparatus according to claim 1 , wherein the money item sensor is located in proximity to a money item guide path to determine the at least one property of the money item moving along the money item guide path.

6. The apparatus according to claim 1 , wherein the money item is electrically conductive.

7. The apparatus according to claim 1 , wherein the resonant electrical oscillator circuit is configured to trigger changes in the oscillating frequency synchronously with an instant of zero electrical current in the resonant electrical oscillator circuit.

8. The apparatus according to claim 7 , further comprising:

one or more capacitors configured to, at the instant of zero electrical current, store electrical energy in the resonant electrical oscillator circuit.

9. The apparatus according to claim 1 , further comprising a controller configured to select a new oscillating frequency of the oscillator.

10. The apparatus according to claim 9 , wherein the controller is further configured to provide an indication of the new oscillating frequency to the oscillator.

11. The apparatus according to claim 10 , wherein the resonant electrical oscillator circuit is configured to trigger a change to the new oscillating frequency in response to receiving the indication of the new oscillating frequency from the controller.

12. A method of sensing properties of money items, the method comprising:

causing, by a controller in a money item sensor comprising a resonant electrical oscillator circuit operable at a plurality of different oscillating frequencies, the resonant electrical oscillator circuit configured to:

trigger one or more switches to change an oscillating frequency by switching one or more capacitive components out of the resonant electrical oscillator circuit synchronously with a beginning of a new half-cycle of the resonant electrical oscillator circuit, wherein when switched out of the resonant electrical oscillator circuit the one or more capacitive components store electrical energy from the resonant electrical oscillator circuit; and

trigger said one or more switches to further change the oscillating frequency by switching said one or more capacitive components back into the resonant electrical oscillator circuit synchronously with a beginning of a further new half-cycle of the resonant electrical oscillator circuit, wherein upon said one or more capacitive components being switched back into the resonant electrical oscillator circuit to adopt a particular configuration of the resonant electrical oscillator circuit an amplitude of the oscillating frequency matches an amplitude of the oscillating frequency when the resonant electrical oscillator circuit was previously in the particular configuration.