--- a/doc/Rvinterf-tools	Wed Jun 07 00:20:26 2023 +0000
+++ b/doc/Rvinterf-tools	Wed Jun 07 07:51:49 2023 +0000
@@ -125,6 +125,15 @@
 	shot" is sent; the default is 7 s.  Specify -w 0 to disable this hack
 	altogether.
 
+-X <virtual LCD program>
+
+	This option exists only to support an obsolete interface for virtual LCD
+	output, originally implemented as an experiment in 2015 and never used
+	with much success.  The program named with this option (the intended
+	usage is -X fc-lcdemu) will be launched via popen(3), and any received
+	output from the target on FC-invented EXTUI RVTMUX channel will be
+	forwarded to this program.
+
 Client programs
 ===============