...and to get the fault signal to trip the latching relay, you can wire the fault outputs from the drivers in series with the estop switches, and any fault output or estop operation will trip the relay. I have three driver fault outputs and three estop switches all wired in series and it works a treat. It's that easy. The set of "switches" are wired into the supply to the relay and you just have to watch the polarities of the fault outputs when you wire them in.