online / offline

They are states or conditions of a "device or equipment" or of a "functional unit". To be considered online, one of the following must apply to a device:

• Under the direct control of another device
• Under the direct control of the system with which it is associated
• Available for immediate use on demand by the system without human intervention

In contrast, a device that is offline meets none of these criteria (e.g., its main power source is disconnected or turned off, or it is off-power).