Which of the following devices requires calibration as part of its installation?

Touch screen digitizers use a grid of sensors that must be aligned to the display coordinates through a calibration process; without it, touch input registers at incorrect positions on screen, rendering the device unusable. Windows includes a built-in touch screen calibration utility (Tablet PC Settings) specifically for this post-installation step, making calibration a defined requirement.

A mouse uses relative movement tracking via an optical or mechanical sensor and translates motion into cursor delta values; no calibration to absolute screen coordinates is required.

An external HDD is a plug-and-play storage device recognized automatically by the OS via USB or eSATA; it has no positional or sensor data requiring calibration.

A keyboard is a simple input device where each key sends a fixed scan code to the OS; no calibration is needed, only optional key remapping through software.