diff --git a/ubb-la/README b/ubb-la/README
index be6f75f..aa939b7 100644
--- a/ubb-la/README
+++ b/ubb-la/README
@@ -70,6 +70,27 @@ When the trigger is present, it takes roughly 550 +/- 250 ns plus one
 sample time until the first sample is taken.
 
 
+Graphical output
+----------------
+
+A graphical interface is available for exploration of a captured
+pattern. This interface is invoked if the option -g is set. Note
+that sample rate, trigger, etc., still have to be set up via the
+command line. Example:
+
+# ubb-la -f 12 -t 0/8 -g
+
+In the GUI, the following keys are available:
+
+  Left/Right	Pan the waveform left/right
+  Up/Down	Zoom in/out
+  Space		Set the user origin (upward-facing green triangle)
+		at the current position and display the time to
+		the center position (downward-facing blue triangle).
+		Pressing space again removes the user origin.
+  Enter/Q	Quit
+
+
 Known bugs
 ----------