How is an interlaced scanning pattern generated in a fast-scan (NTSC) television system?

Interlaced scanning is a clever technique used in analog NTSC television to reduce on-screen flicker without increasing the required transmission bandwidth. A complete 525-line frame is divided into two separate halves known as "fields." To generate this pattern, the electron beam first draws all the odd-numbered lines from top to bottom. Then, it returns to the top of the screen to draw the even-numbered lines, filling in the gaps. Distractors suggesting scanning from bottom-to-top or alternating left-to-right directions are incorrect, as analog TVs always sweep left-to-right and top-to-bottom.