Chapter 6: Two Switch Scanning
Two Switch Scanning (Step Scan) gives the user more control over timing.
How it works
- Switch 1 (Advance): Move to next item
- Switch 2 (Select): Choose current item
One-switch step scanning is possible, but requires a dwell time or mode-switching, and is harder to learn.
Why It Helps
Step scanning removes timing pressure. The user advances at their own pace, which can reduce errors and frustration.
Comparison: Auto-Scan vs Step Scan
| Feature | Auto-Scan (1 Switch) | Step Scan (2 Switches) |
|---|---|---|
| Timing control | System controls | User controls |
| Cognitive load | Must watch timing | No timing pressure |
| Physical effort | 1 switch | 2 switches |
| Speed | Fixed | Variable (user-paced) |
| Best for | Single switch users | Users with good motor control |
Step Scan Alternation (Swap Switch)
Some systems swap switch roles after each selection to balance physical load.
This helps reduce fatigue when one switch position is more tiring than the other.
Demo
🎮 Use Key “2” to advance and Space to select.