Komatsu PC138USLC Operation & Maintenance Manual page 92

OPERATION
Service Meter/Clock Display Selector Switch
On the standard screen, it is possible to press switch F4 to switch
the service meter and clock display at the top of the monitor
display.
When the time is being displayed, press switch F4 to switch to
the service meter display.
When the service meter is being displayed, press switch F4 to
switch to the time display.
DETAILED CONTROLS AND GAUGES
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