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ITGlossary · Communication and monitoring
USB HID (Power Device Class)
Standard USB device class through which a UPS appears in Windows and macOS as a battery, without installing any drivers.
Technical level:Intermediate
Most modern UPS units with a USB port implement the HID Power Device class. As soon as the cable is connected, Windows shows a battery indicator as on a laptop, while macOS adds UPS settings to its power options. On Linux the same UPS is usually recognised through NUT.
Without extra software, the computer can shut down automatically when the UPS battery drops below a threshold. This is enough for a single computer or a NAS, but not for several servers.
In Windows, check that the action for the critical battery level is set to shut down or hibernate and not to “Do nothing”. If the UPS is not recognised, try another cable or port and avoid USB hubs.
Related terms
- Offline (Standby) UPSA UPS that leaves the load on the mains and switches to battery only when the mains fails, with a short transfer time; the simplest and cheapest topology.
- Input Voltage WindowThe range of mains voltage within which a UPS keeps powering the load from the grid without switching to battery.
- Ethernet Port (RJ45)The UPS's Ethernet network port, through which it can be monitored and controlled from any computer on the network via a browser, SNMP or shutdown software.
- SNMPA standard network protocol used to monitor and control devices like UPS systems over a network.
- Alarm ContactA relay output on a UPS that changes state on an alarm, such as battery mode, low battery or a fault, to alert an external system.
- Charging Power (kW)How much energy flows into the battery per hour, which in AC charging depends on voltage, current and the number of phases.