This window provides useful feedback to the ringer both during and after ringing. What is not evident from the static image shown here is that the graphic scrolls smoothly during ringing to provide a constant reference. After ringing (or during) the ringer's own line can be superimposed on the perfect blue line and provides a great way to address specific mistakes in the striking. Errors bars (blue for early, red for late) show the magnitude.
In the above image, for example, the ringer (ringing the 2nd to a course of Grandsire Triples) is consistently holding up too much when leaving the lead, but nevertheless failing to reach the back on time, before holding up too much again prior to coming back down. These errors can be pointed out in an entirely objective way that is immediately clear to the ringer.
The rows themselves are hidden in the above image, but they can be shown when needed.
The graphic can be scrolled up or down throughout the range of the ringing and it can be shrunk or expanded using the zoom control on the control panel. Both scrolling and zooming can be performed using touchscreen gestures if your screen and OS supports this.
The numbered circle at the top representing your own bell is highlighted. You can choose a different bell at any time when the bells are stood.
You can also choose more than one "user bell", in which case you can either focus on one of them at a time or show all the lines at the same time:
The control panel provides two special buttons that change the mode of use of the Blue Line window: