RS232 help

I need help determining the proper pinout between a modem and PLC and a modem and a BM85 Mux. I've tried various arrangement but with no change. I guess the first questions for clarity are:

1. Is the PLC (Quantum Unity 310) to modem (ATL 6410IQ)a DTE to DCE connection? That is my understanding and assumption.
2. What is the type of connection between the BM85 and Modem? I've assumed a DTE to DCE connection but is it a DCE to DCE connection.

I'll leave it at that for the moment.

Thanks

I haven't used a BM-85 for years, do they still make them?
Pins 2 & 3 are Tx and Rx It's very easy to tell which is which because Tx has voltage on it when referenced to ground Rx is at zero.
You make up a cable that marries Tx on one device to Rx on the other with ground to ground.
I have found setting the baud rate low e.g. 1200 then using a terminal program on a laptop helps troubleshoot a new connection. If you set the BM85 to spit out characters then use the terminal program changing the settings until you see sensible characters from the BM85s Tx terminal.
Then you can switch to the modems Tx terminal and do the same thing. Once you know they are both talking the same speed etc then you plug together.
If you leave the shell off the connector you can now see voltage on pin 2 and on pin 3.
You can also connect your laptop to either Tx or Rx and monitor traffic.
BTW you can also use your RS-232 laptop to monitor RS-422 or 485 if you connect to the Tx- wire and ground.
Hope this helps
Roy