Yes, it is true sine. Double conversion, AC to DC to charge the batteries, and then the DC to AC with full time sine wave. It's always running from the batteries, so when the AC fails there is absolutely 0 cut-over time.
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Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris