SHT 10K Manual Del Usuario página 27

CVCF mode Description
LCD display
Battery mode Description
LCD display
When the output frequency is set to "CF", the inverter will output constant
frequency (50 Hz or 60 Hz). At this mode, the UPS will have no bypass
output but still charge battery.
When the input voltage/frequency is beyond the acceptable range or power
failure, UPS will backup power from battery and alarm will beep every 4
seconds.
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