| 摘要 |
<p>A coin 12 to be checked is passed through a test coil 1 connected in parallel with a capacitor 2. A comparison coil 3 having an adjustable core 5 is also connected in parallel with a capacitor 4 and a direct current is passed through both coils in parallel from a rail 13 to an interrupter 14. The simultaneous interruption of the current through both coils produces between each coil and its capacitor a respective oscillatory discharge in the form of a decaying wave train and the characteristics and dimensions of the two coils and their capacitors are such that when a coin of the selected denomination passes through the test coil, the two wave trains are substantially identical. The two wave trains are compared by a comparator device 6 and a voltage comparator 7 generates a signal when the result of the comparison is below a predetermined datum, thus indicating that the coin is a genuine one.</p> |
