A UPS (Uninterruptible Power Supply), also known as an emergency power supply, is designed to provide power to your devices during a power outage. When you are not at home and a power interruption occurs, the UPS will continue to operate and supply power to the connected devices, such as your modem, router, computer, or other essential electronics connected to the UPS.

The UPS is powered by an internal battery that is charged when power is available. During a power outage, the UPS automatically switches to battery power to ensure that the connected devices continue to function. The duration of power supply depends on the capacity of the UPS and the power consumption of the connected devices.

It is important to note that the UPS has a limited power reserve and is not intended to bridge long-term outages. The duration of the power supply varies depending on factors such as the capacity of the UPS, the power consumption of the connected devices, and the age and condition of the battery.

If you are not at home during a power interruption and want to ensure that your devices continue to operate even if the UPS battery runs out, you might consider taking additional measures, such as installing a standby generator or engaging an external monitoring service that alerts you about any power interruptions.

It is advisable to consult the manual of your specific UPS model for detailed information about its operation and capacity so you can have the right expectations about the UPS's performance during power outages.