The IRS motors are controlled by a battery-backed-up microprocessor in the IRS DCU. The motor positions are known unless the motors are moved by hand or there is a major system failure. Thus, it should not be necessary to reinitialize the motor controller during normal observing even if the Sun computer is rebooted. If for some reason the motor controller does need to be reinitialized you can use the command initmtrs. Before invoking this command you should go up to the IRS and note the reading of the Durant counters (4 numbers in all; entrance mirror, aperture wheel, filter wheel and grating drive). The initmtrs command will prompt you for the Durant counter readings and for the gratings which are on side A and B of the grating drive. (The support scientist will tell you which gratings are installed and where.) After this the motor control is initialized but you will have lost the ``jogs'' you may have used to align the slit either spatially or to set the grating zero point. The jog commands move the motor while not altering the position recorded in the memory of the motor control microprocessor. Thus, they reset the zero point for a mechanism.