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5.0 Operation
5.1 Modes of operation
The UPS operates in one of five modessleep, standby, on-line, on-battery, and
bypass-depending upon the condition of the UPS, the batteries, the loads, and the
input mains voltage.

5.1.1 Sleep mode

In sleep mode, the UPSs display is inactive and no voltage is present at the output.
The UPS is put to sleep manually when commanded Off by the user. The UPS
automatically enters sleep mode after 5 minutes with no commands given while in
standby mode (see following section). After 5 minutes, the UPS enters sleep mode
from on-battery mode when shut down because of battery exhaustion or overload, to
conserve battery capacity. Press any front-panel button to awaken the UPS.
Some versions of PowerChute plus allow remote users to put the UPS to sleep and
awaken it after a set interval.

5.1.2 Standby mode

While in standby mode, the UPSs display and control interface is active, but no
voltage is present at the output. The UPS enters standby mode when first awakened
from sleep mode.

5.1.3 On-line mode

Once commanded to power the loads, the UPS is normally in on-line mode. While in
this mode the UPS delivers power derived from the mains to the loads, maintains
proper battery charge, regulates the output voltage to within a narrow band, and
isolates the load from surges and electrical noise brought by the service wiring. A
multilevel transformer tap changing circuit provides this regulation and isolation while
maintaining extremely high efficiency. When adjusting the load voltage, the UPS
temporarily operates the load from battery power while it makes an appropriate
transformer tap change. Remote on-battery signaling is disabled during a tap change.
The UPSs display indicates the percent of rated load applied at the output when
operating on-line.

5.1.4 On-battery mode

When in on-battery mode, the UPS supplies load power derived by the UPSs inverter
from the Battery Packs. The voltage waveshape delivered in on-battery mode is a
low-distortion sine wave. While on-battery, the UPS regulates the output voltage and
frequency to within a narrow band. The UPS operates in on-battery mode during the
user-defeatable start-up or scheduled battery tests. The UPS operates on-battery when
the line voltage or frequency has fallen outside the limits given in the Specifications
section or has become extremely distorted by, for example, noisy adjacent service
branch loads or an overburdened fuel generator source.