[quesera]

Corroborated!

Back-UPS stepped sine wave has about 3 square steps above or below zero, so it's a very rough approximation of a sine wave. Adequate for many kinds of equipment, but ugly on a scope.

There is, or used to be, a pin on the Smart-UPS line that you could tie high (or low?), to tell the device to operate in "Online" mode (inverter always active, line power continuously tending the battery). APC also sold it preconfigured that way as a separate, more expensive, product. :)

There's also a trick to jump-starting an unplugged-but-charged Smart-UPS. I've used this for several hours of remote power in inconvenient locations.

Quality devices, but test them regularly. The switch from idle to high-draw can be violent, and it takes out weak components. Similar to tungsten lightbulb filaments.