Appendix A The Serial Port; The Eia-232 Interface - US Robotics 002805-00 Getting Started

Appendix A
The Serial Port
Most computers provide a DB-25 or DB-9 port that conforms to
the EIA-232 standard. If you are connecting the Courier to a
Macintosh computer, see the section For Macintosh Computers.

The EIA-232 Interface

The Courier's serial port is factory set to signal according to the
EIA-232 standard:
Figure A-1. Signals at the Courier's Serial Port.
The Serial Port A-1