Hello, This feature is very rare but very interesting : using Time and sales you calculate the volume per price level and not the classical volume per bar. A spectrum bar is drawn on the right of the screen near each price level. The longer the bar the more volume there has been on this price level. A spectrum bar is calculated for all the bars displayed on the screen so when you extend the graph to get more bars the spectrum information changes also. The use ? Find real support & resistance Volume is always refering to a bar, the spectrum shows the volume per price level .