英語聽力文摘 錄像機(jī)工作原理

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VCR-盒式磁帶錄像機(jī)VCR是Video Cassette Recorder的縮寫盒式磁帶錄像機(jī)。就功能上而言，它是使用空白錄像帶并加載錄像機(jī)進(jìn)行影像的錄制及存儲(chǔ)的監(jiān)控系統(tǒng)設(shè)備。VCR作為許多晚會(huì)盛典的重要環(huán)節(jié)和收視利器,可以突破演出現(xiàn)場(chǎng)的局限、拓展真實(shí)的情感時(shí)空,能夠承上啟下、營(yíng)造氛圍和升華主題,起到獨(dú)特的藝術(shù)效果?，F(xiàn)在的VCR多指一個(gè)視頻片斷。

Ever wondered how VCRs function? Learn about them on this Moment of Science.

Although audio tapes(錄音磁帶) and video tapes(錄像磁帶) look different, they’re based on the same principles. Each has a roll of (1)magnetic material which slides past the so-called “playback head(放音磁頭)” in the VCR or cassette deck(盒式磁帶錄音座) (cassette decks have one playback head, VCRs have two or more).

In both machines, these heads detect changes in magnetism as the tape moves by. The changing magnetic signal is translated into music on your tape deck(磁帶卡座), or both video and sound on your VCR. Without a changing magnetic signal over a playback head, you’d get no sound, no picture.

But here’s a mystery: When you press pause on the VCR, the screen doesn’t go blank. Instead, you get a frozen image. Remember, you need a changing magnetic signal to create even a still video image. If the video tape isn’t moving, where is this changing signal coming from?

We’re used to VCRs doing this, but it’s actually kind of strange. It would be like (2)pressing pause on a cassette deck and having the sound remain in your (3)speakers, Pavarotti(帕瓦羅蒂(意大利男高音歌唱家)) holding his high C until you press play again. VCRs do this trick by moving both the tape, AND the playback heads, which spin rapidly past the tape as it moves through the machine.

Pausing a video tape does indeed stop the tape, but it doesn’t stop the spinning playback heads. These continue to swipe past the stationary tape, detecting enough of a magnetic signal for one still frame of video. Modern, hi-fi VCRs(高保真錄像機(jī)) automatically mute the sound when they are paused, so you don’t get a sustained audio sound as well!

Notes:

(1)magnetic [m?ɡ'netik] adj.地磁的;有磁性的;有吸引力的

Earth was once magnetic only, and shall return to a magnetic only energy flow.

地球曾經(jīng)是單一磁性的，并將返回到單一磁性的能量流。

(2)pressing ['presi?] 緊迫的;迫切的;懇切的

Increasing or reducing displayed value by pressing button or .

按下或按鈕可使顯示數(shù)值增加或減少。

(3)speakersn. 揚(yáng)聲器;發(fā)言者(speaker的復(fù)數(shù));演說家

Speakers using reflectors to widen the dispersion are not new.

發(fā)言者使用反射來擴(kuò)大分散并不是新的。