Each frame is composed of two fields. One field of video is created when the CCD is scanned across and down exactly 262 ½ times, and this is reproduced on your monitor. A second scan of 262 ½ lines is exactly one-half of a line down and interlaced with the first scan to form a picture with 525 lines. When these two fields are properly synchronized and interlaced in a 2:1 ratio, they form a complete still frame of video.
CCTV cameras use AC voltage to synchronize this process of creating motion video. In countries like the US that use 60 Hz (cycles) alternating current, each second of video contains 60 fields, which forms 30 frames. In Europe and other regions using 50 cycles, there are 50 fields and 25 frames of video per second. To the human eye, these frames of video appear as moving images.
The total voltage produced is one volt from the bottom of the sync pulse to the top of the white level, hence one volt peak-to-peak (p/p). The signal's luminance element is from 0.3 volts to one volt, so the maximum is 0.7 volts. This is known as a composite video signal because the synchronizing and video information are combined into a single signal.
