Horizontal retrace - Display Devices
In a refresh CRT monitor, the time it takes for an electron beam to return to the left most point on the next horizontal line after refreshing one horizontal line is called horizontal retrace. The beam is shut off, blanked, during the period of retrace. Generally, about 83% of the total horizontal retrace time is spent tracing the line. The remaining 17% is spent bringing the beam back to the left side, before starting the next line.