Physically, the disk of an encoder with 2000 counts/rev has 2000 lines for channel A and 2000 lines for channel B.
There are 3 encoding modes : 1) X1 encoding --> only rising edges of one channel --> 2000 counts/rev 2) X2 encoding --> rising and falling edges of one channel --> 4000 counts/rev 3) X4 encoding --> rising and falling edges of both channels --> 8000 counts/rev See also pages 3-18 to 3-20 in the <a href="http://digital.ni.com/manuals.nsf/websearch/DD0DBB6404BC139886256721007CF16D?OpenDocument&node=132100_US";>user manual</a> of the PCI-660X.
