Solution:

The MTBF is 163611. This is Based on MIL 217F using Parts Count Reliability Prediction Method. For the isolation basically there is power coming into the 485DRCi-PH, and the power goes through two separate isolation transformers. They bring power to the RS-232 side and the other brings power to the RS-485 side. It is what we call triple isolation in that the incoming power is isolated form both data sides, and the two sides RS-232 and RS-485 are isolated from each other. Here is a partial schematic: 485DRCi-PH partial schmatic.pdf Here is an additional tech note on the 485DCRi-PH Control Drawing Class 1 Div 2 FOSTCDRI-PH-xx-5110cwd.pdf