text: <s>[INST] Safe Torque Off monitoring with redundant output Summary: I am using a PF755 w/ STO option and want to maintain a Safety Category 3. The STO board's inputs are SP+ and SE+. In Logix 5000 I am planning on using the redundant output instruction (1734-OB8S) w/ one output going to SP+ and the other going to SE+ and the Hardware Enable at TB1-1. The manual says that there is not a monitoring contact w/ the STO. Do i need a monitoring contact for use with the Feedback 1 and Feedback 2 to maintain Safety Catagory 3? If not, should i use anything on FB1 and FB2? [/INST] It depends on whether or not you have your PF755 connected to the Logix platform to use CIP motion or if it is connected as a regular drive. In CIP motion, you are not permitted to use any of the drive I/O cards. As a regular drive, you are. You could then task one of the outputs to be the monitoring contact. I agree with you, Rockwell made a mistake not putting the monitoring contact on the STO card. \\n </s>