Considering secure environments, the internal memories of the MS4640A series VNA uses DRAM (Dynamic Random Access Memory) in its CPU board and Flash Memory in its DSP (Digital Signal Processing) board. The disk drive in new units is an easily removable SATA Solid State Drive (SSD). Older units have an easily removable Hard Disk Drive (HDD).

The DRAM is used by the CPU for temporary memory purposes and all the information is lost upon powering off the unit, which is characteristic of dynamic memory.

Flash Memory is used to save instrument factory calibrations and settings. No user application information is stored in Flash Memory and the memory space is not user-accessible. Since this memory space is not used by the user, nor by the instrument to store user application settings, it does not require cleansing after it has entered a Secured Location.

The current Solid State Drive (SSD) (and the older Hard Disk Drive or HDD) are fully accessible by the user to store configuration data and measurements including instrument saved setups, custom presets, last used setups, and similar information. For secure applications and locations, the SSD can be easily and quickly removed from the instrument chassis and left in the Secure Location. The chassis can then be moved to another location and another optional SSD installed. The SSD/HDD is accessible from the rear panel, and can be removed by loosening two screws, sliding the drive out, and then unplugging the connector cable, allowsing the VNA case chassis can then be transferred to another location.

When operation in secure environments is planned, the recommended option is to purchase one or more of the MS4640A-004 Additional Solid State Drive assemblies. The Option 004 SSD supplies a separate assembly that is loaded with the proper factory configuration data and information. By using the Option 004 SSD, the VNA can then continue to be used in both outside non-secure and inside secure environments. Multiple Option 004 SSDs can be used to facilitate support of multiple secure locations.