| 摘要 |
<p>The unit is comprised of a feed device (11, 13), an effacement head (16), a read device (15) and a control device. A light source (18) and at least two light sensors (20, 21) of the read device are arranged at a side of a recording support, the effacement head (16) being arranged on the other side. During the effacement process, the read device (15) is in operation. The output signals of the light sensors (20, 21), connected to a comparator, change in the opposite direction upon the effacement of a mark. The control device interrupts the effacement process as soon as the output signal of the comparator exceeds, respectively, goes down under a predetermined level. The effacement head (16) has a heating element which may be moved away from the recording support, a heating element with low heat capacity which may be disconnected or a projection lamp as a thermal radiation source. The feed device is comprised of a step motor, a screw (11) and a card support (13). </p> |
