Brother HL 1240 - B/W Laser Printer Service Manual page 255

How to use the SERIAL INTERFACE (RS-100M)
Connection (For HL-1250 Only)
To connect the printer to a DOS computer with a serial interface or to an Apple
Macintosh computer with a serial interface, you need to install the optional serial
interface board (RS-100M). When you have installed the serial interface board, you
can share the printer between two computers (two IBM compatible PCs or one IBM
compatible PC and one Apple Macintosh) using the parallel and serial interfaces at
the same time. Automatic interface selection between the two connections is a
standard feature.
Note
The serial interface board for this printer is an option, but in some countries the
serial interface board may have been installed by either the factory or dealer.
The serial interface for Apple Macintosh (RS-422A) will only print at 300 dpi.
The serial interface board is installed onto the main controller board inside the
printer. For installation details, see the instruction guide which is provided with the
serial interface board.
2-3
CHAPTER 2 OPTIONS