diff --git a/library/RSL_Emulation.ttcn b/library/RSL_Emulation.ttcn
index a42ca1e..7c5a168 100644
--- a/library/RSL_Emulation.ttcn
+++ b/library/RSL_Emulation.ttcn
@@ -1,5 +1,22 @@
 module RSL_Emulation {
 
+/* RSL Emulation, runs on top of IPA_Emulation.  It multiplexes/demultiplexes
+ * the individual connections (logical channels), so there can be separate TTCN-3 components
+ * handling each of the connections.
+ *
+ * The RSL_Emulation.main() function processes RSL messages from the IPA demultiplex
+ * stack via the IPA_RSL_PT, and dispatches them to the per-connection components.
+ *
+ * Outbound RSL connections are initiated by sending a RSLDC_ChanRqd primitive
+ * to the component running the RSL_Emulation.main() function.
+ *
+ * (C) 2017 by Harald Welte <laforge@gnumonks.org>
+ * All rights reserved.
+ *
+ * Released under the terms of GNU General Public License, Version 2 or
+ * (at your option) any later version.
+ */
+
 import from General_Types all;
 import from Osmocom_Types all;
 import from GSM_Types all;