| 摘要 |
<p>A holding circuit for a vending machine incorporating a money/card tester 24, and having a control circuit 14 with a parallel interface which processes a vend only when signals are simultaneously received from both a user operated selection switch 26, for choosing the vend item, and the tester, upon validation of the deposited tender, comprises a holding relay 42 which provides a continuous signal to the control circuit once the selection button has been pressed, and a means of sending a reset signal 48, 50 to the holding relay from the tester or the control circuit. The tester contains a microprocessor 16, the control circuit comprises a sales relay 28 for determining the vend price, and the coupling between the various elements may be via opto-couplers 22, 32. Preferably a time function element 38, controlled by the control circuit, is provided and resets the holding relay after a pre-set time. An AND gate (60, Figure 2) may also be provided so that signals from both the time function element and from the control circuit signifying that a vend has occurred (40, Figure 2) are required to reset the holding relay. The holding circuit thus takes account of the time delay, which may be several seconds, necessary for the testing of charge or smart cards and hence ensures a vend even if the operator does not depress the selection switch for the whole of this time period.</p> |
