问题
问答题 简答题
常用的脉冲信号波形有哪三种？
答案
参考答案：
1）、短波形2）、三角波3）、锯齿波
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常用的脉冲信号波形有哪三种？
参考答案：
1）、短波形2）、三角波3）、锯齿波
Lego, the inventor of those colorful bricks that have inspired kids’ imaginations world-wide, has celebrated its 50th anniversary.  On January 28, 1958, a man named Godtfred Kirk Christiansen created the plastic building bricks that can now be found in almost every child’s toy box. The simple building block has become one of the most well-known and popular toys around the world. "The Lego brick continues to be very attractive, because it allows children, and others, to develop their creativity and imagination," said Charlotte Simonsen, a spokeswoman of the Danish Lego company. The company’s building brick allows an infinite number of links. With just two bricks there are 24 different links, and with six, there are 915 million possibilities, according to Lego. A half-century after its creation, more than 400 million children and adults spend five billion hours a year putting the bricks together and pulling them apart. Also, the bricks made today can still interlock with those made in 1958. Lego bricks are not just child’s play: they also attract the interest of adults. South Korean adventurer, Heo Young-Ho, who climbed Mount Everest in 1987, left a Lego toy behind in the snow during his climb. After its great success Lego experienced a severe crisis at the end of the 1990s, hit hard by fierce competition from electronic games. This so-called "Toy of the Century" then suffered a dark period that lasted several years. With great efforts, the company began to prosper again, and in 2006 it earned about 1.5 billion dollars in 130 countries. Seven boxes of Lego are now sold every second around the world, and 19 billion bricks are produced each year: enough to encircle the Earth five times！ 小题1:The Lego bricks have remained popular in the past 50 years as a result of _______.
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