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录像机是用来记录、重放图像和声音信号的。它与录音机虽具有相似的原理,但无论在机械部分还是电路部分都要比录音机复杂得多。因为图像信号的信息量远大于音频信号的信息量,所以录像机不能采用录音机那样的固定磁头来进行录放,而是采用旋转磁头来增加磁头与磁带的相对速度,以进行高密度的记录和重放,如图1所示。PAL制1/2英寸VHS盒式录像机的相对速度为484cm/s,磁带速度为2.339cm/s,磁头的旋转速度为1500r/min。为了确保磁带运动速度、磁头旋转速度的准确性,录像机内设有磁头鼓电机和主导轴电机伺服控制电路。
VCRs are used to record, play back images and sound signals. Although it has a similar principle with the recorder, it is much more complicated than the recorder in both the mechanical part and the circuit part. Because the amount of information of an image signal is much larger than the amount of information of an audio signal, a VTR can not use a fixed head such as a recorder for recording and reproducing. Instead, a rotary head is used to increase the relative speed of the head and the tape for high-density recording and reproduction ,As shown in Figure 1. The PAL 1/2 "VHS VTR has a relative speed of 484 cm / s, a tape speed of 2.339 cm / s and a head rotation speed of 1500 r / min. In order to ensure the speed of the tape movement and the accuracy of the head rotation speed, a head drum motor and a capstan motor servo control circuit are provided in the video recorder.