Add some more explanatory text.

usr.bin/mixerctl/mixerctl.1

@@ -1,4 +1,4 @@
-.\" $NetBSD: mixerctl.1,v 1.6 1998/04/27 16:55:23 augustss Exp $
+.\" $NetBSD: mixerctl.1,v 1.7 1998/05/09 12:37:42 augustss Exp $
 .\" Copyright (c) 1997 The NetBSD Foundation, Inc.
 .\" All rights reserved.
 .\"
@@ -84,6 +84,43 @@ The
 flag shows the possible values of enumeration and set valued
 variables.  Enumerated values are shown in [] and set values
 are shown in {}.
+.Pp
+The exact set of controls that can be manipulated depends on
+the mixer.  The general format (in both getting and setting a value)
+is
+.br
+.Va "class.name" = value
+.br
+The
+.Va class
+can have values like
+.Li inputs
+or
+.Li outputs
+indicating that the control affects the input resp. output to the
+mixer.  The 
+.Va name
+indicates what part of the mixer the control affects.
+Continous mixer values, e.g., volume, have numeric values
+in the range 0-255.  If value can be set for each channel independently
+the values are printed separated by commas.  Discrete mixer values, e.g.,
+the recording source, have symbolic names.  Depending on the mixer it
+may either be an enumeration or a set.
+.Sh EXAMPLES
+The commmand
+.Dl "mixerctl -a -v"
+can produce
+.Bd -literal
+inputs.mic=0,0 volume
+inputs.mic.mute=off  [ off on ]
+inputs.cd=220,220 volume
+inputs.cd.mute=off  [ off on ]
+inputs.dac=220,220 volume
+inputs.dac.mute=off  [ off on ]
+record.record=220,220 volume
+record.record.source=mic  [ mic cd dac ]
+monitor.monitor=0 volume
+.Ed
 .Sh FILES
 .Bl -tag -width /dev/mixer
 .It Pa /dev/mixer