閉路電視
Multi tool use
“监视器”和类似名称重定向至此。
閉路電視（英语：Closed-Circuit Television，簡稱CCTV）是指在特定的區域進行視訊傳輸，並只在固定迴路設備裡播放的电视系统。例如錄影機、大樓内的監視器等。這類播放模式就被稱作閉路電視。
以前有些人[谁？]會稱錄影機播放節目叫做閉路電視，不過在錄影機普及后这种说法日渐式微，反倒是大樓的監視系統目前還會被稱作閉路監視系統。
它與廣播電視不同，儘管也是點對點进行連接，但閉路電視的信號非公開傳輸。全球第一部閉路電視是於1942年在德國開始使用[1]，用於觀察V-2火箭的發射。
广义上的“闭路电视”在中国大陆通常称“监控探头”，而中国所谓的狭义上的“闭路电视”则指的是“有线模拟电视”。在中国海外的报道中，很多会将“闭路电视”简称为“CCTV”（非指中国中央电视台）。
爭議
随着在公共場所安裝的閉路電視數量不斷增加，這也導致了一些關於侵犯私隱而引發的訴訟。有些人更將閉路電視用於個人、私隱或者商業用途。
用途
閉路電視通常用於需要監測的領域，例如銀行、賭場、機場、軍事基地、校園、警察局和便利商店等。
在商業領域，閉路電視系統可以從一個中央控制室注意到其它不同區域的情況。例如有些地方不適宜人親自去監控，則可以安裝閉路電視系統連續的錄影或者按照指示只是對某一些特定事件進行監控。
早期的閉路電視系統使用錄影帶做為儲存媒體，近幾年已改用單顆或多顆硬碟做為儲存媒體，省卻更換錄影帶及保存的不便，如果要求更高的錄影容量與反應速度，也有使用磁碟陣列卡來加強錄影儲存能力。
目前閉路電視業發展到一種新的形式，就是用数字视频录像机把影像大量、清晰地錄影下來，保留多年，並對保存的影像進行分析或其他操作。
不過，日常物業管理保安影像只保留7天至30天，因為社會有法例規管。在過去不少罪案皆可以由閉路錄影協助破案，例如色魔、高買、打劫等。
參考文獻
^ Walter Dornberger: V-2, Ballantine Books 1954, ASIN: B000P6L1ES, page 14.
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维基共享资源中相关的多媒体资源：閉路電視
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