B&B Electronics QSPXP-100 - Manual - Manual (Page 16)

Making external connections B&B Electronics ExpressCard Serial Adapter User’s Manual
Page 12 Rev 1.00 (July 2007)
Making external connections
The Serial Adapters are equipped with male DB-9 connectors for RS-
232 and with female DB-9 connectors for RS-422/485. The following
figures and tables show the serial port pinouts for RS-232 and RS-
422/485 applications.
RS-232 serial connections
RS-232 devices are classified by their function as either Data
Terminal Equipment (DTE) or Data Communication Equipment
(DCE).
Figure 14 - Use of DTEs and DCEs in a communication link
DTE- and DCE-type devices have complementary pinouts that allow
terminals and modems to connect directly using a one-to-one cable as
shown in Figure 15. Two DTE-type devices can be connected by a
null modem cable. A typical null modem cable is also shown in the
figure.
Figure 15 - Cabling requirements for RS-232 devices
Note: A DTE device is the
communication source. A DCE
device provides a communication
channel between two DTE-type
devices.
Figure 15 illustrates the RS-
232 pinouts for typical DTE-
to-DCE and DTE-to-DTE
cables with 9-pin connectors.
Note: In many applications,
DCEs are unnecessary. This
allows you to use a null modem
cable (modem eliminator cable)
to directly connect two DTE-
type devices.