diff --git a/doc/other.xml b/doc/other.xml
index b530616..f398024 100644
--- a/doc/other.xml
+++ b/doc/other.xml
@@ -1259,6 +1259,12 @@ do not have infinitely sharp cutoffs.
Slowly-varying inputs
+
+Note: The functions described here use an old
+feature that is no longer implemented by the &comedi;
+kernel layer. THEY WILL NOT WORK!
+
+
Sometimes, your input channels change slowly enough that
you are able to average many successive input values to get a
diff --git a/doc/reference.xml b/doc/reference.xml
index 08c4c3b..3d2afb1 100644
--- a/doc/reference.xml
+++ b/doc/reference.xml
@@ -368,7 +368,7 @@ struct comedi_trig_struct{
The comedi_trig structure is a control structure used by the
COMEDI_TRIG ioctl, an older method of communicating
instructions to the driver and hardware. Use of comedi_trig is
-deprecated, and should not be used in new applications.
+deprecated, and is no longer implemented by the &comedi; kernel layer.
@@ -399,8 +399,8 @@ struct comedi_sv_struct{
The comedi_sv_t structure is used by the comedi_sv_…
functions to provide a simple method of accurately measuring
-slowly varying inputs. See the relevant section for more
-details.
+slowly varying inputs. This relies on the COMEDI_TRIG
+ioctl and is no longer by the &comedi; kernel layer.