diff --git a/secop/modules.py b/secop/modules.py
index 63d3aae..c5c26e2 100644
--- a/secop/modules.py
+++ b/secop/modules.py
@@ -305,6 +305,19 @@ class Module(HasProperties, metaclass=ModuleMeta):
                 pass
 
     def registerCallbacks(self, modobj, autoupdate=()):
+        """register callbacks to another module <modobj>
+
+        - whenever a self.<param> changes:
+          <modobj>.update_<param> is called with the new value as argument.
+          If this method raises en exception, <modobj>.<param> gets into an error state.
+          If the method does not exist and <param> is in autoupdate,
+          <modobj>.<param> is updated to self.<param>
+        - whenever <self>.<param> gets into an error state:
+          <modobj>.error_update_<param> is called with the exception as argument.
+          If this method raises an error, <modobj>.<param> gets into an error state.
+          If the method does not exist, and <param is in autoupdate,
+          <modobj>.<param> gets into the same error state as self.<param>
+        """
         for pname in self.parameters:
             errfunc = getattr(modobj, 'error_update_' + pname, None)
             if errfunc:
diff --git a/secop_psi/softcal.py b/secop_psi/softcal.py
index 7b4e405..c45cd39 100644
--- a/secop_psi/softcal.py
+++ b/secop_psi/softcal.py
@@ -51,7 +51,7 @@ class StdParser:
         self.xdata, self.ydata = [], []
 
     def parse(self, line):
-        """get numbers from a line and put them to self.output"""
+        """get numbers from a line and put them to self.xdata / self.ydata"""
         row = line.split()
         try:
             self.xdata.append(float(row[self.xcol]))