Sierra Wireless DART 200 CDPD Modem - Manual (Page 89)

DART 200 CDPD Modem User’s Guide 6 Device Attachment
PN1197-00 Revision 1.0 6-3
To identify this problem connect a PC directly to the device and establish
communication. If communication is established, the device uses a DCE
interface and requires a null modem to communicate with the DART
200.
Null modem adapters are available as stand-alones; that look like an
RS-232 gender-changer, or as null modem cables. Null modem adapters
are available from electronics stores and are well suited for application
development. Null modem cables can be ordered from cable suppliers,
and are better suited for field deployment, because the cables eliminate
the extra part and failure prone connections required for a stand-alone
null modem.