Question E2B02:
How many horizontal lines make up a fast-scan (NTSC) television frame?  

Choices:  
A: 30  
B: 60  
C: 525  
D: 1080    

Correct Answer is  C: 525  

Correct answer: C — 525

Why C is correct:
- Fast-scan ATV using the NTSC standard uses 525 horizontal lines per frame. Of these, about 480 are visible; the rest are in the vertical blanking interval.

Why the others are incorrect:
- A: 30 — This is the frame rate in frames per second for NTSC ($\approx 30$ fps), not the number of lines.
- B: 60 — This is the field rate in fields per second for interlaced NTSC ($\approx 60$ fields/sec), not the number of lines.
- D: 1080 — This is the line count for HDTV 1080i/p formats, not NTSC.

Useful relationships and rules of thumb:
- NTSC interlaced video:
  - Lines per frame: $525$
  - Fields per second: $\approx 60$ (actually $59.94$)
  - Frames per second: $\approx 30$ (actually $29.97$)
  - Lines per field: $$\frac{525}{2} = 262.5$$
  - Relationship: $$\text{Frames/sec} = \frac{\text{Fields/sec}}{2}$$
- Quick memory aid: NTSC = 525/60/30; PAL = 625/50/25.