diff --git a/src/plotcontrolpanel.h b/src/plotcontrolpanel.h
--- a/src/plotcontrolpanel.h
+++ b/src/plotcontrolpanel.h
@@ -40,9 +40,12 @@ public:
     ~PlotControlPanel();
 
     unsigned numOfSamples();
-    bool autoScale();
-    double yMax();
-    double yMin();
+    bool   autoScale() const;
+    double yMax() const;
+    double yMin() const;
+    bool   xAxisAsIndex() const;
+    double xMax() const;
+    double xMin() const;
 
     void setChannelInfoModel(ChannelInfoModel* model);
 
@@ -53,7 +56,8 @@ public:
 
 signals:
     void numOfSamplesChanged(int value);
-    void scaleChanged(bool autoScaled, double yMin = 0, double yMax = 1);
+    void yScaleChanged(bool autoScaled, double yMin = 0, double yMax = 1);
+    void xScaleChanged(bool asIndex, double xMin = 0, double xMax = 1);
 
 private:
     Ui::PlotControlPanel *ui;
@@ -74,6 +78,8 @@ private slots:
     void onAutoScaleChecked(bool checked);
     void onYScaleChanged();
     void onRangeSelected();
+    void onIndexChecked(bool checked);
+    void onXScaleChanged();
 };
 
 #endif // PLOTCONTROLPANEL_H