Changing of alarm and control levels on analogue signals and controllers. 改變模擬信號和控制器的警報及控制水平。
Unlike analogue signals, which tend to degrade gradually when digital signals drop data, the picture can freeze abruptly. 模擬信號往往會逐漸劣化,數字信號不同,它丟失數據后,畫面會突然靜止。