If you do not code the UCS parameter, the system checks the UCS image in the printer’s buffer; if it is a default image, as indicated by its first byte, JES uses it. If it is not a default image, JES loads the UCS image that is the installation default specified at JES initialization.

On an impact printer, if the chain or train does not contain a valid character set, JES asks the operator to specify a character set and to mount the corresponding chain or train.