diff --git a/load_tariff b/load_tariff
index b6e9413..55af161 100755
--- a/load_tariff
+++ b/load_tariff
@@ -1,6 +1,23 @@
 #! /bin/bash -
 # set -x
 
+#
+# echo "Usage: ./${0##*/} <tariff.config> <tariff.current>"
+#
+# tariff.config: a JSON-file representing the tariff which should be used
+#                (this tariff-file is generated by a web-based tool of 
+#                 Mobilisis)
+# tariff.current: a file containing infos about the currently used tariff:
+#               VERSION: version of the tariff
+#               PROJECT: e.g. szeged
+#               ZONE: usually 1
+#               INFO: additional info for the tariff (optional)
+#               LOADED: date when tariff has been loaded
+#
+#               This file will be used by the update_psa-script to send
+#               a message to ISMAS containing the current settings of the PSA.
+#
+
 if [ $# -eq 2 ]; then
     if [ -f $1 ]; then
         out="\"VERSION\":\"$(cat $1 | jq -r .version)\"",