Solution:

Two siturations are shown as below: A. RS-485 connector <==> ADAM-4000 series Check Data+/Data- connect to ADAM-4000 series properly. Besides, make sure the baudrate and ID address setting of ADAM modules are correct. You also need to guarantee I/O address and IRQ don't conflict with other device. After that, you can use ADAM.EXE to check the communication. B. RS-232 connector <== ADAM-4520 ==> ADAM-4000 series 1. Connect ADAM-4000 modules to PCL-740 with correct wiring method. 2. Make sure the setting of SW2 inside the ADAM-4520 is correct. For example, you want to use 2400 bps to communicate with ADAMs, you need to adjust DIP 3 of SW2 to on position and other dips go to "Off" position. 3. Change the baudrate of ADAM I/O module to the proper configuration. You need to connect INIT* to GND first, then re-power on this module, click [Setup] label under ADAM.EXE to set the baudrate. After that, power off and remove the wire between INIT* and GND, then reboot again. 4. When you start ADAM utility to search ADAM modules, you need to change the baudrate under this utility to fit ADAM modules. 5. If you are sure the baudrate settings of ADAM utility, ADAM-4520 and ADAM I/O modules are the same, we believe the communication will be all right.