Haas Alarm: 679 (M) TT or B ZERO RET MARGIN TOO SMALL – This alarm will occur if the home/limit switches move or are misadjusted. This alarm indicates that the zero return position may not be consistent from one zero return to the next. The encoder Z channel signal must occur between 1/8 and 7/8 revolution of where the home switch releases. This will not turn the servos off, but will stop the zero return operation.