GB765071A - A method of and apparatus for detecting and rejecting spurious coins from a vending machine - Google Patents

Abstract

765,071. Testing coins electcically. YELLAND, L. J. Oct. 15, 1952 [Nov. 2, 1951], No. 25833/52. Class 37. [Also in Group XVIII] Testing coins : electric and magnetic properties.-The unbalanced voltage from an inductive bridge, whose balance is affected by the presence of a coin to be tested, is applied to a detector whose output depends on the phase of the unbalanced voltage relative to the input to the bridge as well as on its magnitude. This is stated to permit adjustment to pass valid coins of two different mints. The coin 16 (Fig. 3) to be tested, and a standard coin 15, are supported in similar gaps 12, 11 in the laminated core 9, 14 of a transformer, the primary 17 of which is connected to the A.C. mains. The secondaries 18, 19 of the transformer are connected in series-opposition and coupled by a condenser 79 (Fig. 2) to the grid 76 of a valve 75 the anode 74 of which is direct-coupled to a triode 64. When an invalid coin is under test the out-ofbalance voltage from secondaries 18, 19 raises the anode potential of valve 75 sufficiently to cause the current drawn by the anode of triode 64 to operate a relay 66 which prevents actuation of a vending machine. A condenser 81 connected across the secondaries 18, 19 may be adjusted so that, when a valid coin of higher conductivity than the standard coin 15 is under test, the ripple on the grid 76 is in phase with the voltage on the anode 74 and maintains the current drawn by the anode 74 sufficiently high to prevent operation of the solenoid 66.