A UPS (Uninterruptible Power Supply), also known as an emergency power supply, is designed to provide your devices with power during a blackout. When you are not at home and a power outage 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 charges when power is available. During a power outage, the UPS automatically switches to battery power to ensure the connected devices keep working. The duration of the power supply depends on the UPS's capacity 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 power outages. The duration of the power supply varies depending on factors such as the UPS's capacity, the power consumption of the connected devices, and the age and condition of the battery.

If you are not at home during a power outage and want to ensure that your devices keep working even if the UPS battery runs out, you may consider taking additional measures such as installing a generator or using an external monitoring service that notifies you of any power outages.

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 correct expectations about the UPS's performance during power outages.