| 摘要 |
<p>PURPOSE:To reduce power consumption by using the difference of light transmissibility between a transparent tape and a magnetic tape on tape start and end terminal parts to detect a disturbance light level, and when the level is low, controlling a tape start and end terminal detector so that the sensitivity of a photodetecting element is increased and current flowing into a light emitting element is reduced. CONSTITUTION:To detect the tape start and end terminals, the disturbance light level is detected at first. In order to detect said level, a low level signal is sent from an output terminal 9 of a microcomputer 7 to turn off a current amplifier 8 and then turn off the light emitting diode LED1. Subsequently, a low level signal is sent from an output terminal 11 of the microcomputer 7 so that the sensitivity of a phototransistor PQ1 is increased and only low current is made flow into a light emitting diode LED1, and then the output of the 1st voltage comparator 2 is read from an input terminal 13 of the microcomputer 7 at the timing synchronizing with the period that the light emitting diode LED1 is on. The transparent tape is detected by changing the sensitivity of the phototransistor PQ1 and the current flowing into the light emitting diode LED1 in accordance with the strength of the influence of disturbance light.</p> |
