diff --git a/Usage.md b/Usage.md
index fbbdd7a..2b12ad3 100644
--- a/Usage.md
+++ b/Usage.md
@@ -18,6 +18,8 @@ Example:
 
 Note you may mount multiple drives at a time.
 
+If no image files are found PC13 will pulse on and off.
+
 # Termination
 
 To enable termination place the two jumpers on the TERM block. Termination should be enabled if it is the last device in the chain - which is normally how it is used.
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