| 摘要 |
<p>The apparatus for detecting a perforated postage stamp on envelopes travelling in a given direction comprises a light source to illuminate the teeth of a perforated edge of the stamp at a right angle to the given direction; a scanning device receiving light from the illuminated edge of the stamp and producing a high frequency pulse train responsive to scanning the teeth of the illuminated edge of the stamp; and an evaluating circuit responsive to the pulse train to provide an indication of the presence of the stamp.</p> |
