diff --git a/frappy/mixins.py b/frappy/mixins.py
new file mode 100644
index 0000000..2945604
--- /dev/null
+++ b/frappy/mixins.py
@@ -0,0 +1,92 @@
+#  -*- coding: utf-8 -*-
+# *****************************************************************************
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Markus Zolliker <markus.zolliker@psi.ch>
+#
+# *****************************************************************************
+
+from frappy.datatypes import BoolType, EnumType, Enum
+from frappy.core import Parameter, Writable, Attached
+
+
+class HasControlledBy(Writable):
+    """mixin for modules with controlled_by
+
+    in the :meth:`write_target` the hardware action to switch to own control should be done
+    and in addition self.self_controlled() should be called
+    """
+    controlled_by = Parameter('source of target value', EnumType(members={'self': 0}), default=0)
+    inputCallbacks = ()
+
+    def register_input(self, name, deactivate_control):
+        """register input
+
+        :param name: the name of the module (for controlled_by enum)
+        :param deactivate_control: a method on the input module to switch off control
+        """
+        if not self.inputCallbacks:
+            self.inputCallbacks = {}
+        self.inputCallbacks[name] = deactivate_control
+        prev_enum = self.parameters['controlled_by'].datatype.export_datatype()['members']
+        # add enum member, using autoincrement feature of Enum
+        self.parameters['controlled_by'].datatype = EnumType(Enum(prev_enum, **{name: None}))
+
+    def self_controlled(self):
+        """method to change controlled_by to self
+
+        to be called from the write_target method
+        """
+        if self.controlled_by:
+            self.controlled_by = 0
+            for deactivate_control in self.inputCallbacks.values():
+                deactivate_control(self.name)
+
+
+class HasOutputModule(Writable):
+    """mixin for modules having an output module
+
+    in the :meth:`write_target` the hardware action to switch to own control should be done
+    and in addition self.activate_output() should be called
+    """
+    # mandatory=False: it should be possible to configure a module with fixed control
+    output_module = Attached(HasControlledBy, mandatory=False)
+    control_active = Parameter('control mode', BoolType())
+
+    def initModule(self):
+        super().initModule()
+        if self.output_module:
+            self.output_module.register_input(self.name, self.deactivate_control)
+
+    def activate_control(self):
+        """method to switch control_active on
+
+        to be called from the write_target method
+        """
+        out = self.output_module
+        if out:
+            for name, deactivate_control in out.inputCallbacks.items():
+                if name != self.name:
+                    deactivate_control(self.name)
+            out.controlled_by = self.name
+        self.control_active = True
+
+    def deactivate_control(self, switched_by):
+        """called when an other module takes over control"""
+        if self.control_active:
+            self.control_active = False
+            self.log.warning(f'switched to manual mode by {switched_by}')