Classic Computer Magazine Archive COMPUTE! ISSUE 59 / APRIL 1985 / PAGE 111

IBM Graphics Printer Switch Settings

Michael A. Covington

Although neither the IBM PC reference manuals nor the instructions that come with the printer mention them, the IBM Graphics Printer has a set of internal DIP switches which allow you to control how it operates.

The switch settings within the IBM Graphics Printer determine the defaults that apply when the printer is first turned on; almost all of them can be overridden by sending appropriate escape codes to the printer. But there may be situations in which you'll want to change the defaults.
    To get at the switches, unplug the printer, disconnect the interface cable, remove the plastic cover and wire-grid paper guide, and turn the printer upside down. Unscrew the four Phillips-head screws at the corners, then put tape over the deep holes they sit in so they won't fall out. Now turn the printer right side up, pull off the paper advance knob, and carefully lift off the cover, maneuvering it clear of the knob shaft.
    On the main circuit board you should find two sets of DIP switches under removable plastic dust covers. Using a ballpoint pen or similar tool, set them according to your preference (see accompanying table), put the dust covers back in place, and reassemble the printer.
    The most useful thing the switches can do for you is give you access to the full character set. The IBM PC Guide to Operations lists two character sets for the printer; in character set 1, ASCII codes 128 to 159 are duplicates of codes 0 to 31, but in character set 2, they are accented letters for foreign languages. (Both character sets include a variety of mathematical symbols and box-drawing characters.)
    A few programs may not work properly with character set 2; if you have this problem, you can either set the switch back to its original setting, or set the printer back into character set 1 by sending it ASCII codes 27 and 55 as an initialization sequence.

IBM Graphics Printer Internal Switch Settings
Asterisks mark how switches are set at the factory.

A. Large set of 8 switches:
1 Not used; normally on.
2 Off: Printer generates a linefeed of its own
after every carriage return.
 *On: Printer does not advance to next line
until it receives a linefeed character
(ASCII 10).
3 *Off: When more characters are received than
will fit on a line, printer begins a new
  On: When more characters are received than
will fit on a line, printer overprints on
same line.
4 *Off: ASCII code 24 clears the printer buffer.
   On: ASCII code 24 has no effect.
5 Not used; normally on.
6 Off: Buzzer on printer will not sound.
 *On: Buzzer sounds when out of paper or
when ASCII code 7 is received.
7 *Off: Character set 1.
    On: Character set 2.
8 Off: Computer sends "Select" signal to
activate printer.
  *On: Printer is always ready to receive input.

B. Small set of 4 switches:
1 *Off: Paper length is 11 inches.
    On: Paper length is 12 inches.
2 *Off: Lines are spaced 6 to the inch.
    On: Lines are spaced 8 to the inch.
3 *Off: Paper feeding is controlled by computer.
   On: Paper automatically advances after
4 *Off: Printer does not skip over the perforation
where pages join.
   On: Printer skips 1 inch where pages join.