This example shows how to create custom widgets with signals and slots, and how to connect them together in more complex ways. ... int value() const; public slots: void setValue( int ); signals: void valueChanged( int ); . ... Let's look at what happens when the user operates the scroll bar: The scroll bar sees that its value has changed, and emits the valueChanged() signal. That signal is connected both to the display() slot of the QLCDNumber and to the valueChanged() signal of the LCDRange. ...