why a digital signal is better that an analog signal, but what makes DTV a “high-definition” format?
For starters, let’s examine how the current NTSC image is created on your TV at home. A television image is created with a series of horizontal lines that are “drawn” by an electron gun that “shoots” a beam of energy onto the phosphor on the inside of the picture tube’s face. When the beam hits the phosphor, the phosphor glows and a television image is created. In the current NTSC system, the total number of lines drawn by the electron gun is 480. These images are drawn 60 times a second, though not all of the 480 lines are drawn at this rate. The NTSC system is interlaced, meaning that the full 480-line frame is drawn in two separate fields consisting of 240 lines each. All of the odd-numbered lines are drawn on the first pass (the first 1/60th of a second). The even-numbered lines are drawn on the next pass (the next 1/60th of a second), completing the picture. This system can be referred to as “480i,” where “480” is the total number of lines that make up the picture and “i” indicate
