Final answer:
The NTSC television system specifies 525 scanning lines, with roughly 480 lines being visible due to the interlaced scanning process. The NTSC system was the standard analog television system in North America, using a 4:3 aspect ratio, until the transition to digital broadcasting.
Step-by-step explanation:
The NTSC (National Television System Committee) television system specifies 525 scanning lines. However, due to the nature of interlaced scanning, only about 480 lines are visible on the screen, with the remaining lines making up the vertical blanking interval (the time it takes for the scanning electron beam to move from the bottom of the screen back up to the top). The NTSC system is an analog television system that was once widely used in North America and other parts of the world before the shift to digital broadcasting.
The NTSC standard uses a 4:3 aspect ratio, and the number of scanning lines is a critical component that determines the resolution of the broadcasted image. With the advent of digital television, newer standards such as ATSC have taken over, offering higher resolutions and more scanning lines, leading to better picture quality.