Radio Shack PRO-96 Owner's Manual page 91

The "CPU" and "DSP-Voc" firmware versions are permanently installed at time of
manufacture and cannot be updated in the field. The "DSP-App" version is field
upgradeable. The original factory version is indicated by "F" preceding the version
number. The DSP-App version number will be preceded by "U" after the DSP version
is updated via Internet download.
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