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Appendix B - Cabling Considerations Serial Console (RS-232)
36 Mosport 1TE/2TE
Serial Console (RS-232)
DTE or DCE
A device that communicates over a synchronous serial interface is either a DTE (Data Terminal Equipment)
or DCE (Data Communications Equipment) device. DTE devices usually connect to DCE devices. The
Mosport 1TE/2TE and a PC are a DTE, while a CLI terminal is a DCE.
Crossover Cable (Null Modem)
The crossover version of the DB-9 cable (also known as null modem) uses a female-to-female cable in any
application where you wish to connect the Mosport 1TE/2TE with another DTE device such as a PC or
workstation. This cable is required for CLI application.
The purpose of a null-modem cable is to permit two RS-232 “DTE” devices to communicate with each other
without modems or other communication devices (i.e., DCEs) between them.
To achieve this, the most obvious connection is that the TD signal of one device must be connected to the RD
input of the other device (and vice versa).
Figure 18: DB-9 Crossover Connectivity
2- RX
3- TX
5- GND
TX -2
TX -3
GND -5
7- SG
8- CD
SG -7
CD -8
6- DSR
1- DCD
4- DTR
DSR -6
DCD -1
DTR -4
4- DTR DTR -4