| 摘要 |
<p>An opto-electronic end-of-tape sensor has a pulsed light source for producing high intensity, short duration light pulses and a photodetector controlling a clock driven digital counter. In a normal condition with tape blocking the light pulses, the counter is kept in a reset state. If a clear light path of sufficient time duration is detected the photodetector output enables the counter to reach a predetermined count to obtain an end-of-tape signal output. The sensor circuit discriminates against pinholes in the tape by requiring detection of an uninterrupted predetermined number of light pulses to generate the end-of-tape signal.</p> |
