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- An impulse that, in a neutral circuit, causes the loop to open or causes absence of signal. In a polar circuit it causes the loop current to flow in a direction opposite to that for a mark impulse. A space impulse is equivalent to abinary zero. 在中性电路中，引起环路断开或造成信号消失的一种脉冲（信号）。在极性电路中，空号脉冲促使环路电流向传号脉冲相反的方向流动。空号脉冲相当于二进制零。
- The two systems of government are polar opposites. 这两种政体正好相反。
- Most insect do not live in polar region. 大多数的昆虫不在极地地区生存。
- There are two breakers in this circuit. 这个电路里面使用了两个断路器。
- A replaceable printed circuit board. 一种可替换的印制电路板。
- Are there any animals in the polar circles? 南极圈和北极圈内有动物存在吗？
- The circuit of the city walls is three miles. 环绕本市城墙的周长是三英里。
- Located or found in one of the Polar Regions. 环极的，围绕极地的位于或发现于一个极地区域中的
- There must be a break in the circuit. 电路中一定有断路。
- A short circuit will blow the fuse. 短路会烧断保险丝的。
- A short circuit put the machine out of action. 短路使机器停转。
- In spite of vigilance a polar bear escape from the zoo. 尽管警戒很严，北极熊还是逃出了动物园。
- The switches close the contacts and complete the circuit. 这些开关可使接触器接通电流形成回路。
- The polar region is the habitat of the polar bear. 北极地带为北极熊的栖息地。
- Although they can swim, the polar bears are terrestrial animals. 北极熊虽然会游泳，但也是陆栖动物。
- In spite of vigilance a polar bear escaped from the zoo. 尽管警戒很严，北极熊还是逃出了动物园。
- The polar bear's habitat is the icy waters of the Arctic. 北极熊的栖息地是冰冷的北极海域。
- Love and hatred are polar feelings. 爱与恨是完全相反的感情。
- Don't connect up the two wires, or there will be a short circuit. 不要把这两条电线接在一起，否则会短路的。
- The rocket did one circuit of the earth and returned to base. 火箭绕地球运行一周后返回基地。
