In the 6k Soft. Ref Guide page 76 and the 6k Prog Guide page 69, it talks about the EFAIL command. It states that "if there is no active signal on either phase A or phase B of an axis encoder(i.e. encoder is fully disconnected).....". This is incorrect. The 6K only detects a failure if phase A detects a high signal on both A+ and A-. The B channel is not checked. A+ and A- are internally pulled to +5V and if both of these signals are high, then the fault occurs (if EFAIL is enabled). A failure could occur if either A+ or A- are disconnected, it depends on whether the other signal was high or low at that time.