Chapter 2: The Bandwidth Problem
Input Bandwidth refers to the amount of information a user can transmit per unit of time.
| Input Type | Bandwidth | Speed |
|---|---|---|
| Touch Typist | High (10+ fingers) | ~100 words/minute |
| Hunt & Peck | Medium (1-2 fingers) | ~20 words/minute |
| Switch User | Low (1 binary input) | ~5-15 words/minute |
Switch access lives at the lowest end of the bandwidth spectrum. Scanning compensates by trading time for access.
The Sushi Bar Analogy
Imagine a sushi bar where dishes rotate past you on a conveyor belt. You cannot reach everything at once—you must wait for the dish you want to come to you, then grab it quickly.
Switch users trade TIME for ACCESS. They don’t have instant access to any item like a mouse user. They must wait for the scan to reach the item they want, then activate their switch at precisely the right moment.
Interactive Sushi Counter
REACH ZONE
Sushi Conveyor
Dishes rotate past you. You cannot reach everything.
Wait for the dish to enter the red Reach Zone, then click it.
It gets faster every time you eat.
Speed: 2
Takeaway
Scanning is slow but powerful. It gives full access to large selection sets with a single switch—just not instantly.