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-rw-r--r--sys-utils/hwclock.8.adoc5
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diff --git a/sys-utils/hwclock.8.adoc b/sys-utils/hwclock.8.adoc
index 3e181ed..0b23a37 100644
--- a/sys-utils/hwclock.8.adoc
+++ b/sys-utils/hwclock.8.adoc
@@ -101,6 +101,11 @@ The first two are only available on the first call of *settimeofday*(2) after bo
*-w*, *--systohc*::
Set the Hardware Clock from the System Clock, and update the timestamps in _{ADJTIME_PATH}_. With the *--update-drift* option also (re)calculate the drift factor. Try it without the option if *--systohc* fails. See *--update-drift* below.
+*--vl-read*, *--vl-clear*::
+Some RTC devices are able to monitor the voltage of the backup battery and thus provide a way for the user to know that the battery should be replaced. The *--vl-read* function retrieves the Voltage Low information and decodes the result into human-readable form. The *--vl-clear* function resets the Voltage Low information, which is necessary for some RTC devices after a battery replacement.
++
+See the Kernel's _include/uapi/linux/rtc.h_ for details on which pieces of information may be returned. Note that not all RTC devices have this monitoring capability, nor do all drivers necessarily support reading the information.
+
include::man-common/help-version.adoc[]
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