In case your voltage amounts are unstable (ie: power stays on, but the actual voltage degree differs a great deal with the 220V standard), then I think that's the sort of circumstance exactly where an AVR is helpful. A UPS unit on your router and modem can also be good https://felixcbxxp.tinyblogging.com/helping-the-others-realize-the-advantages-of-uninterruptible-power-supply-cyberpower-77480583