To protect a modem from power outages and maintain a stable internet connection, a UPS (Uninterruptible Power Supply) can be used. When choosing a UPS for a modem, there are several important factors to consider:

1. Capacity: Ensure that the UPS has enough power to supply the modem and any other connected devices. Check the power consumption of the modem and select a UPS with an appropriate capacity.

2. Runtime: The runtime of the UPS determines how long the modem will be powered during a power outage. Choose a UPS with a sufficiently long runtime to ensure that the modem can continue to operate for the desired time.

3. Connections: Check whether the UPS has the correct connections to connect the modem. Most modems can be connected via a standard power outlet. Ensure that the UPS has the necessary outlets or connections for the modem.

4. Additional features: Some UPS models offer additional features, such as surge protection, data line protection, and software for UPS management. These features can further enhance the protection of the modem.

Well-known brands of UPS systems include APC, Eaton, CyberPower, and Tripp Lite. It is advisable to compare the specifications and features of different UPS models and choose a UPS that meets the specific needs of your modem and other devices you want to protect.