IBM 3101 Dip Switches Configuration

Hello. I have one IBM 3101 ascii terminal ready to be used connected with one serial cable to one Linux system that I have by the serial port 2. The inittab has uncommented the line referred to the ttyS1, and appears to be correct because one "ps -ef" shows the "/sbin/agetty ttyS1" line with the "[login]" comment. The problem is that the IBM 3101 don't establish communication with the Linux system. The 3101 show one "Line Check 2" message that talk about the comm.line, I suppose. The cable used is one normal serial cable. The 3101 has some dip switches in the upper of the keyboard. If they are taked, the Line Check 2 message dissapears and the screen is filled with "?" signs continuously. It's clear that some options can be configured with this method. Somebody has some more deep info about this terminal ? Must I use one special serial cable ? Thanks and Greetings Sergio