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在最近十五年内。使用磁带(Videotape)放映教学资料和图片已甚风行。十年前又有磁盘(Videodisc)问世。目前在美国已有四分之一的公立中学和大学具备一种或多种的磁盘放映机,且其数字在继续增加,不久可能代替磁带的使用。磁带和磁盘在教学上有同样的价值和功能。使用者可以控制放映的快慢、程序、甚至内容。这两种放映机的价格相似,需用的有关电子设备的费用也相似。但它们也有明显的差异: (一)磁盘放映机较为牢固,可以使用四千小时而无故障,磁带放映机在使用过五百小时后即有产生故障的可能。 (二)磁盘本身可以持续十年不坏。通常磁带的平均寿命
In the last fifteen years. The use of video tapes (Videotapes) to teach teaching materials and pictures is very popular. Ten years ago there was a Videodisc. Already, a quarter of public high schools and universities in the United States have one or more disk projectors, and their number continues to increase, possibly replacing the use of tapes in the near future. Tape and disk have the same value and function in teaching. Users can control the show’s speed, program, and even content. The price of these two projectors is similar, and the cost of the related electronic equipment required is similar. However, they also have obvious differences: (1) The disk projector is relatively firm, can use four thousand hours without any trouble, and the tape projector has the possibility of generating a failure after it has been used for 500 hours. (B) the disk itself can last ten years is not bad. Average tape life expectancy