| 摘要 |
Coin discrimination apparatus comprises a path (1) for passage of coins under test; sensor coils (2, 3, 4) forming an inductive coupling with a coin under test during its passage along the path, each of the sensor coils being connected in a resonant circuit (10, 11, 12) which exhibits a resonant frequency that varies in dependence upon the inductive coupling between the coil and coin, control circuitry (14) which maintains the resonant circuit at the resonant frequency while a coin under test is inductively coupled to the coil, and amplitude responsive circuitry (MPU) responsive to the change in the amplitude of an oscillatory signal developed by the resonant circuit when the coin under test passes the sensor coil to discriminate between different coins, wherein the control circuitry includes a zero crossing detector (A1) responsive to the oscillatory signal crossing a zero threshold level for producing a rectangular waveform corresponding to the oscillatory signal, and drive circuitry (FF1, 2; OR1, 2) responsive to said rectangular waveform for driving the resonant circuit to maintain resonance.
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