diff --git a/ld2dap/Filter.py b/ld2dap/Filter.py
index 01cb13e..fa21c66 100644
--- a/ld2dap/Filter.py
+++ b/ld2dap/Filter.py
@@ -14,7 +14,3 @@ from Output import Output
 class Filter(Input, Output):
     def __init__(self):
         super().__init__('Filter')
-
-    def _run(self):
-        print('ima not virtual!')
-
diff --git a/ld2dap/Output.py b/ld2dap/Output.py
index 007e695..bd2b5cc 100644
--- a/ld2dap/Output.py
+++ b/ld2dap/Output.py
@@ -26,5 +26,12 @@ class Output(Node):
         if not isinstance(inode, (Input)):
             raise NotImplementedError('{} is not an Input'.format(inode))
         self.__dict__['input'] = inode
+        inode.register(self)
+
+    def process(self, data):
+        self._process(data)
+
+    def _process(self, data):
+        raise NotImplementedError('{} should override _process()'.format(self))
 
 
diff --git a/ld2dap/test.py b/ld2dap/test.py
index ba2bb55..d8643ea 100644
--- a/ld2dap/test.py
+++ b/ld2dap/test.py
@@ -20,6 +20,8 @@ def main():
     print(n.input)
     n.input = f
     print(n.input)
+    print(f.outputs)
+    f.process(None)
 
 if __name__ == '__main__':
     main()