Refer to figure.
In their normal navigation mode, the IRSs provide attitude, true and magnetic heading, acceleration, vertical speed, ground speed, track, present position, and wind data to appropriate aeroplane systems. IRS outputs are independent of external navigation aids.

• The Inertial System Display Unit (ISDU) is typically located on the aft overhead panel and displays data according to the position of the display selector and system selector. The ISDU also contains a keyboard for entry of present position and heading.
• The Mode Select Unit (MSU) is also normally located on the aft overhead panel and is used to select the operating mode for each IRS. Indicator lights on the MSU show status of each IRS. The IRS control unit provides a control knob with the positions OFF, ALIGN and NAV for normal operation and the ATT mode for reduced performance operation. The IRS control panel features individual controls for every IRU.

Note: The attached figure depicts the IRS control unit of the Boeing 737NG.