a) A frame consists of all the information required for a complete picture. For interlaced scan systems, there are two fields in a frame. For progressive video, these lines contain samples starting from one time instant and continuing through successive lines to the bottom of the frame.

b) A complete picture composed of two fields. In the NTSC system, 525 interlaced horizontal lines of picture information in 29.97 frames per second.

In the PAL system, 625 interlaced horizontal lines of picture information in 25 frames per second. c) The metal cabinet which contains the switcher’s circuit boards. d) One complete video image, containing two fields. There are 30 frames in one second of NTSC video.