A single track of slots patterns the periphery of an incremental encoder disk, as shown in Figure 1. These
slots create an alternating pattern of dark and light lines. The disk count is defined as the number of
dark/light line pairs that occur per revolution (lines per revolution). As a rule, a second track is added to
generate a signal that occurs once per revolution (index signal: QEPI), which can be used to indicate an
absolute position. Encoder manufacturers identify the index pulse using different terms such as index,
marker, home position, and zero reference