Sony HKDW-704 Operation Manual page 127

USER CODE
Displays the user code.
When you this item, the USER CODE window appears.
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Enter the 4-byte alphanumeric strings for user identification.
The user code is registered with each organization locally. It is usually
not centrally registered.
When the country code is less than 4 bytes, enter the country code from
the beginning of the 4 bytes and enter the space character (20h) in the
remaining strings.
This user code is determined by the organization. The methods used
depends on the organization.
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Chapter 2 Using UMID Data