Index: trunk/BNC/bnchelp.html
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--- trunk/BNC/bnchelp.html	(revision 1285)
+++ trunk/BNC/bnchelp.html	(revision 1289)
@@ -642,5 +642,5 @@
 </ul>
 <p>
-Note that in RTCM Version 2.x the message types 18 and 19 carry only the observables of one frequence. Hence it needs two type 18 and 19 messages to transport the observations from dual frequency receivers.
+Note that in RTCM Version 2.x the message types 18 and 19 carry only the observables of one frequence. Hence it needs two type 18 and 19 messages per epoch to transport the observations from dual frequency receivers.
 </p>
 <p>