The power supply had to be mounted inside the garage, as well as the attached battery backup unit. The battery should be good for 8-10 hours in a power failure, and needs to be replaced about once a year at a cost of $22.
The battery backup is necessary to keep phone service running in the event of a power outage. With copper, line voltage is provided by the same line as the phone signal, but you can’t provide power over fiber optic line, thus the need for a battery backup.
If I put my wireless router on a UPS, I could theoretically also still have fiber broadband connectivity during a power outage. I’ll have to test that one out.