Campbell Scientific CR1000 Measurement and Control System - Manual (Page 551)

Appendix C. Serial Port Pinouts
551
Table 125. Standard Null-Modem Cable or Adapter-Pin
Connections*
DB9 DB9
pin 1 & 6 ---------- pin 4
pin 2 ---------- pin 3
pin 3 ---------- pin 2
pin 4 ---------- pin 1 & pin 6
pin 5 ---------- pin 5
pin 7 ---------- pin 8
pin 8 ---------- pin 7
pin 9 XXXXX
pin 9
(most null modems have no connection)
* If the null-modem cable does not connect pin 9 to pin 9, the modem will need to be configured
to output a RING (or other characters previous to the DTR being asserted) on the modem's TX
line to wake the datalogger and activate the DTR line or enable the modem.