IBM Personal Computer AT Manual To Operations page 144

Ready Button and Ready Light
2
Press the Ready button several times and watch
the Ready light go on and off.
Press the Ready button until the Ready light is
on. Your printer is now in the ready mode and
will accept data from the system.
3
4
Try pressing some of the other buttons. Notice
that when your printer is in the ready mode,
none of the other buttons can be used.
5
Press the Ready button again to turn the Ready
light off. Your printer is now in the not-ready
mode and will not accept data from the system.
Note: The Ready light will flash
continuously if your printer is in the ready
mode but has been released by your system.
See "ESC
Q
2" and "DC3" in "Printer
~
Control Codes. "
1-34 Color Printer