B&B Electronics MESR424T_D-MT_D-SC - Manual - Manual (Page 70)

10. Glossary
Appendix D: Connector Pinouts
DB9 Serial Port Pinouts
DB9 M Pin Direction RS-232
1 Input DCD
2 Input RXD
3 Output TXD
4 Output DTR
5 --- GND
6 Input DSR
7 Output RTS
8 Input CTS
9 No Connection