Expensive electronics, such as computers, DVRs, Security Systems, big screen televisions, etc. require a UPS battery backup system to ensure their long life and proper operation. When it comes to your life, things like CPAP Machines, heart rate monitors, and similar critical equipment rely on a clean stream of power. Sure a surge suppressor can catch spikes (voltage or amperage spikes), and transients (lightning strikes) before the fuse is blown. When the fuse is blown though, the power shuts down on your electronics, or medical equipment; abruptly. When this happens during a Hard Disk Drive write sequence, often the hard drive is lost, with all data, and your computer. If your charger says "OUTPUT DC" you are charging a battery for the configuration you see to the right.
Lags (frequency changes), sags (voltage or amperage dips), and temporary power outages occur frequently and are not mitigated with a surge suppressor. To adequately protect you and your electronics, a battery backup is the answer the manufacturer chose. Depending on the size of your battery backup, you can even cut the cord. Your cell phone never has enough of a battery, but now you know what the power cord does, and why you can charge it from anywhere, even dirty power, and it doesn't hurt the electronics inside. You can charge these sensitive electronic with a generator or secondary source including solar, wind, and hydro power.
You can run a DC Television from a generator without lines going through it.
You can remove the hum from your stereos both at the mobile concert, and in your home theater.
This format of hard wired Uninterruptable Power Supply System, UPS for short, and battery backup for understanding sake, runs your electronics until the power in the battery runs out. Charge it up, and it comes back on. The size of the battery bank, and the alternative charging equipment on hand dictate your runtime.
The PUC says the average American has 120 power "disruptions" per year.
Do you really trust that surge protector to make power in the middle of the night?
The better answer is a Battery Backup System.