Epson 486SX - Manual (Page 27)

5. Plug the printer’s power cord into a properly grounded
(earthed) electrical outlet.
Using the Serial Interface
If you have a printer, a modem, or other peripheral device with
a serial interface, you can connect it to the serial (RS-232C) port
on the back of the computer.
The serial port has a DB-9P connector, so be sure you have a
compatible cable. To connect a serial device, follow the same
steps as above for connecting a parallel device, but insert the
connector into the serial port, marked with a special icon, as
shown below.
Note
Additional steps may be necessary to set up the serial port so
it functions properly. If you are using the port for a printer,
you need to direct printer output to the serial port, not the
parallel port. To do this, you can use the MS-DOS MODE or
SETMODE command. See your MS-DOS manual for details.
Setting Up Your System 1-9