The Digital Comparator Subsystem (DCS) is the predecessor to the SMU and is mainly found with 9500 series systems. DCS units have onboard diagnostics and calibrations that can be accessed using this feature. Firmware for the DCS can also be updated using this feature. When the PC is correctly connected to a DCS, the feature will automatically connect with the DCS when the feature is run. The user will be presented with a main menu from the DCS.
Source: NETS User Manual, Revision D, document 132-06035-0006, section 8.2.3.2.