STANDALONE board includes IOB-21 module and one ribbon cable. Replaces the standard digital inputs and outputs with 8 DI/O points externally mounted with input voltage level of 24...48V DC. The inputs are filtered and galvanically isolated. Terminals X6 & X7 on the main control must not be used when a SDCS-IOB-2x board is installed. Note: If IOB-3 is also required, you must order the combination kit instead (SDCS-IOB-21/IOB-3).