Sun Microsystems Sun PCI High Speed Quad Port Serial Interface Adapter 819-1207-11 - Manual (Page 27)

Chapter 2 SunHSI/U Adapter Installation 7
RS-232 to RS-449 Connections
In order to connect RS-232 devices to the adapter, you need to install an externally
powered RS-449 to RS-232 interface converter to each DB-37 connector on which you
intend to connect an RS-232 device. A converter is necessary because of
incompatibilities between RS-232 and RS-449 signal levels.
To obtain an externally powered RS-232 to RS-449 interface converter, contact:
Black Box Corporation at: http://www.blackbox.com
Note – Use only externally powered RS-449 devices with the SunHSI/U adapter.