Human–computer input devices: which device is often used as an alternative to a light pen and works well with storage-tube or non-refresh displays?

Introduction / Context:
Early graphics systems used light pens for direct interaction with CRTs. However, light pens rely on timing the electron beam refresh—something that storage-tube and certain non-refresh displays do not provide reliably. In such contexts, indirect pointing devices that do not depend on screen refresh proved more effective.

Given Data / Assumptions:

• We are comparing pointing/input devices suitable for graphics work.
• Non-refresh or storage-tube displays make light-pen timing impractical.
• Digitizers (graphics tablets) capture pen position on a separate surface.

Concept / Approach:
A graphics digitiser (digitizer tablet) provides absolute coordinate input using a stylus on a tablet surface. The tablet sends high-resolution x–y positions to the computer, independent of display technology. This makes it a natural alternative to the light pen when the display cannot be sensed directly. Trackballs and mice are relative pointing devices intended for refreshed raster displays and general UI use; they do not solve the refresh dependency. The generic word “tablet” can be ambiguous (modern touch tablets vs. graphics digitizers), so “digitiser” is the precise historical term used in CAD and early graphics workflows.

Step-by-Step Solution:
Identify the requirement: input that does not rely on CRT beam timing.Match device: graphics digitiser meets the need.Exclude relative devices (mouse, trackball) as not ideal for this constraint.

Verification / Alternative check:
Classic CAD setups paired storage-tube or high-persistence displays with digitizer tablets for precise input of points, curves, and selections, confirming suitability.

Why Other Options Are Wrong:
Trackball and mouse rely on relative motion and are not historically the alternative for storage-tube displays. “Tablet” is too vague and may be misinterpreted; the correct, established term is graphics digitiser. “None” is invalid because an appropriate device exists.

Common Pitfalls:
Confusing modern consumer tablets with professional graphics digitizers; the question refers to the latter.

Final Answer:
Digitiser