Physical Controls Are Part of the Reliability Model

The important detail in Physical Controls Are Part of the Reliability Model was not the component name but the contract around it. Call, mute, volume and power are critical actions, so LOUP does not make them dependent on an animated touchscreen interface.

Dedicated physical controls plus a rotary encoder let common actions map to stable input events. The e-paper display can show state and selection without being the only path to answer, mute or change volume. That reduces coupling between UI refresh timing and call control.

The acceptance test was written around observable behaviour rather than whether a task, container or peripheral merely reported that it had started. Evidence marker: physical-controls.

For critical interaction, tactile controls are not nostalgia; they are a fault-containment boundary between input and display behavior. That gives the team a concrete acceptance condition and a rollback point rather than a subjective sense that the build is probably better.

Project evidence

LOUP engineering marker: physical-controls. This note records the design or debugging lesson without publishing device credentials, private keys, customer data or manufacturing secrets.