Epson Apex 20020, 20040 User Manual page 28

To connect a serial device, follow the same steps outlined
above for a parallel device, but connect the cable to the serial
port, shown below.
Setting up the serial port for a printer
If you are using a serial printer but your software does not
support a serial printer, you must do two things before you can
print:
Set up the data transmission parameters for the serial port
Tell the computer to redirect printer data from the parallel
port to the serial port.
The MS-DOS MODE command lets you define the baud rate,
parity, data length, and number of stop bits for a primary and a
secondary serial port. MODE also lets you redirect output from
the parallel port to the serial port. (The MENU program offers
an easy way to use MODE. For instructions, see the description
of the Mode Settings option of the MENU program in your
MS-DOS Reference Manual.)