IBM Personal Computer AT Manual To Operations page 151

By setting DIP (Dual In-line Package) switches 9 and
10 off, you will get the same printout each time you run
the printer self-test. If the printout does not print
correctly, your printer may require service.
22
Close the access cover.
23
Turn your printer's power on.
24
Press the Ready button until the Ready light is
Off.
Note: Paper at least 215.9 mm (8.5 in.) wide
must be installed for the printer self-test.
Color Printer 1-41