GB1375554A - - Google Patents

Abstract

1375554 Testing coins AUTELCA AG 30 Nov 1971 [4 Dec 1970] 55631/71 Heading G4V In a coin tester wherein coins 1 to be tested enter the field coil 2 of the tuned circuit of a feedback oscillator, whereupon depending on the electromagnetic properties of the coin the oscillations do or do not stop, the oscillator amplifier 4 has a negative feedback, the ratio of negative to positive feedback being variable between two values at which an acceptable coin will respectively stop and not stop the oscillations, such that if an acceptable coin is indicated at one ratio then the coin is tested at the other ratio, an acceptance signal for the coin only being issued when the tests at both ratios are satisfied. In the embodiment described the first test is performed at the feedback ratio at which an acceptable coin causes the oscillation to stop (Fig. 2, not shown) which condition is sensed by Schmitt trigger 6 and integrator circuit 7 connected via impedance transformer 8 to control circuit 9. On receiving a signal indicating that the oscillations have been stopped control circuit 9 emits a signal e to change the negative feedback ratio to the value at which an acceptable coin will not stop the oscillations, and if a signal d indicating such is received emits an acceptance signal f on line 92. If however the oscillations are stopped at the second feedback ratio, or are not stopped at the first ratio, a reject signal is emitted on line 93. A circuit diagram of the tester is shown in Fig. 4 (not reproduced). In the rest condition the supply voltage to the tester is reduced and is increased by means responsive to the insertion of a coin. Before the actual test the negative feedback can be set to a third level to determine whether an object to be tested is located in the field coil. Multidenominational tester.-A pretest device for thickness and diameter of inserted coins may be provided, this test determining a suitable pair of feedback ratios for the particular denomination of coin. Cleaning apparatus.-Detectors may be provided at the coin inlet and coin outlet, these being connected to a circuit which causes temporary widening of the coin channel if a signal from the inlet detector is not followed within a predetermined time by a signal from the outlet detector.