| 摘要 |
<p>The frequency-sensing circuit of a paper currency validator uses fixed, rather than adjustable, components to sense a predetermined frequency; and an adjustable speed D.C. motor is set to drive the vertical grid lines in the portrait background of a bill past the air gap of a magnetic head at a selected rate to develop signals of that predetermined frequency. That frequency-sensing circuit is much more stable and much less expensive than a frequency-sensing circuit which uses adjustable components, and that D.C. motor is much smaller and much less expensive than a synchronous motor of comparable power. That D.C. motor causes bill-driving members to move a bill past a bill-actuated switch and then past that magnetic head; and a timing circuit will reverse that motor, to cause those bill-driving members to move that bill back outwardly of that paper currency validator, if that magnetic head does not coact with the frequency-sensing circuit to develop a validation signal within a predetermined length of time. A sub-circuit senses the current flowing to the motor; and, if a person attempts to retard or halt the inward movement of a bill, the value of the motor current will increase, and the current-sensing sub-circuit will respond to the increase in motor current to inhibit the development of a validation signal. The paper currency validator has a bill-actuated start switch, a bill-actuated sequence switch and a bill-actuated exit switch; and those switches are normally connected to the rest of the circuitry of that paper currency validator. However, as soon as a validation signal is developed, all of those switches are immediately isolated from the rest of that circuitry; and this is desirable, because it keeps any further closing of any of those switches from affecting the rest of that circuitry. In this way, any undesirable effect from "contact bounce" or from the deliberate closing of any of those switches is completely obviated. If a person attempts, in an unauthorized manner, to cause the paper currency validator to supply a vend signal, the motor of that paper currency validator will automatically reverse and thereby cause the bill-driving members to return to that person any bill or other object which was being used in that attempt. In addition, that paper currency validator will cancel any validation signal which had been developed as a result of the insertion of that bill or other object. The paper currency validator disposes one magnetic head so it can sense the vertical grid lines in one quadrant of the portrait background of a bill and disposes a second magnetic head so it can sense the vertical grid lines in the diagonally-displaced quadrant of that portrait background; and it requires those magnetic heads to simultaneously supply signals of essentially the same frequency. The paper currency validator disposes bill-driving members immediately outwardly of the first magnetic head, and it also provides a sub-circuit which will reverse the motor if the leading edge of a bill is not able to move a fixed distance beyond that magnetic head within a predetermined length of time. Because those bill-driving elements are disposed immediately outwardly of that magnetic head, they will remain in engagement with the trailing edge of that bill even if substantially the entire length of that bill is wrinkled and crumbled up against that magnetic head; and that sub-circuit will reverse the motor, and thereby enable the bill-driving members to move thaT bill back outwardly of the paper currency validator, before those bill-driving members could tear or otherwise degrade that bill.</p> |
