Comtrol RocketPort EXPRESS, User Manual

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RocketPort EXPRESS User Guide : 2000481 Rev. G Connecting Serial Devices - 11
Connecting Serial Devices
This section provides information about the RocketPort EXPRESS connectors, in
the event that you need to build cables or loopback plugs.
• DB9 Serial Cables and Loopback Plugs on Page 11
• DB25 Serial Cables and Loopback Plugs on Page 14
• RJ45 Serial Cables and Loopback Plugs on Page 17
• RJ11 Serial Cables and Loopback Plugs on Page 19
A loopback plug is a serial port plug with pins wired together that you can use
with an application (for example, the diagnostic, Test Terminal, or minicom) to
test serial ports. See
Before Calling Technical Support on Page 25 for information
about using the test application shipped with the RocketPort EXPRESS.
DTE Versus DCE
Most devices, except modems, are Data Terminal Equipment (DTE) devices.
Modems are Data Communication Equipment (DCE) devices. RocketPort
EXPRESS ports are configured as DTE.
How you build a cable depends on which device your are connecting to (DTE or
DCE). For example, you need a null-modem cable to connect the COM ports
(COM1 or COM2) on the computer or the RocketPort EXPRESS ports to printers,
terminals, bar code readers or DNC equipment. If you are connecting a DTE
device to a DCE device you need a straight-through modem cable.
• Straight-through cable (DTE to DCE) - connects TxD to TxD and RxD to RxD.
• Null-modem cable (DTE to DTE) - connects TxD to RxD and RxD to TxD.
DB9 Serial Cables and Loopback Plugs
The following figures and table illustrate the signals present on DB9 connectors if
you need to build your own null-modem or straight-through DB9 serial cables.
Quadcable, octacable, and the interface boxes use DB9 male connectors.
• DB9 Signals on Page 12
• DB9 Null-Modem Cables (RS-232) on Page 12
• DB9 Null-Modem Cables (RS-422 or RS-485 Full-Duplex) on Page 12
• DB9 Straight-Through Cables (RS-232 or RS-485 Half-Duplex) on Page 13
• DB9 Loopback Plugs on Page 13