四极声源(30)一种分成四部份而相位交替振动的噪音源。
Quadrupole source (30) a noise source in which four parts vibrate alternately in phase.
在PAL制式(相位交替行)标准是在60年代初期提出并在除法国大多数欧洲国家实施。
The PAL (Phase Alternating Line) standard was introduced in the early 1960's and implemented in most European countries except for France.
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