Citizen CT-S801 User Manual page 48

Note:
*: If print data is very dense, the print head is hot, data transmission is slow, or some other conditions,
the motor and printing may occasionally stop which causes white stripes in the printout. To print
high-density data, set MSW2-3 (Spool Print) to ON to reduce striping, although this increases the
time before printing starts.
For a serial interface, increase the transmission speed to prevent the motor from stopping.
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