Apple PC Compatibility Card 7-inch card - Manual (Page 116)

Configuring the PC serial ports
Your PC Compatibility Card supports two serial ports, COM1 and COM2.
You can map these ports to Macintosh serial ports (such as the printer or
modem port) or to a text file for later processing. Or you can leave the
ports unmapped.
m
To map a PC COM port, open the PC Setup control panel and choose a setting in the
COM1 or COM2 pop-up menu.
Macintosh serial ports already in use appear dimmed in the menu.
IMPORTANT Mac OS programs cannot access a port that you’ve assigned to the
PC environment. To use the port in the Mac OS, you must unmap the PC
COM port and restart the PC.
Setting up a modem or other serial device
From the PC environment, you can use a modem or other serial device
connected to the Macintosh serial port.
Because the Macintosh uses the RS-422 protocol, several RS-232 signals are
not available through a Macintosh serial port:
m Carrier Detect (CD)
m Data Set Ready (DSR)
m Request to Send (RTS)
m Ring Indicator (RI)
You can set most communications applications to respond to the CARRIER
string sent back by most modems rather than requiring Carrier Detect. For
more information about using serial ports, see your DOS and Windows
documentation.
104 Chapter 5