双语畅销书《艾伦图灵传》第8章:水银延时线(2)
Alan Turing did not wait to take up the NPL post before thinking about the practical construction of his universal machine.
In particular he discussed with Don Bayley the problem which dominated its engineering—that of the storage mechanism, or 'tape'.
他和唐·贝利一起，讨论过通用机的一个工程问题，即它的存储设备，或者说"纸带"。They discussed every form of discrete storage that they could think of. For instance, they considered magnetic recording.
他们讨论了他们能想到的所有的离散存储形式，比如说磁带。
They had seen a captured German Army 'Magnetophon', the first successful tape recorder,
他们看过一台从德军手中缴获的"玛尼托芬机"，那是最早的成功应用的磁带录机。but rejected the idea essentially because magnetic tape was too much like the tape of the theoretical Universal Turing Machine—it would require so much physical moving to and fro.
但他们从根本上排除了个选项，因为磁带与理论的图灵机模型太像了，它需要来回移动，这会造成很多麻烦注。Instead, they favoured another solution with which Alan was by now well acquainted—that of the 'acoustic delay line.'
图灵现在比较喜欢的方案是"声音延迟线"。The idea was based on the fact that the time taken for a sound wave to travel along a few feet of pipe was of the order of a thousandth of a second.
这个方案的原理是，声波穿过一条几英尺的管道，大约需要千分之一秒的时间。The pipe could be regarded as storing the sound wave for that period.
在这段时间内，可以理解成，这条管道将声波存储在其中。The principle had already been applied in radar, using information stored in the delay line to cancel out all the radar echoes which had not changed since the last scanning.
该原理已经在雷达技术上得到了应用，利用存储在延迟线中的信息，来抵消前一次扫描之后没有发生改变的反射信号。In that way the radar screen could be made to show only new, or changing, objects.
这样一来，雷达屏幕就只显示那些新出现的，或者正在运动的物体。
