Hi Folks, I found this thread in a search, looking for info on the HX702 and a Phase One back. Pulling the "protrusion off the HX702 does allow my P25+ back to functions as a "Large format"-2-shot back. I've adapted a broken Kapture-group box to give me a "Wake-up" signal, by just removing the circuit board, and soldering the momentary switch across the sync cables lines (only 2 lines come from the flash sync on the lenses), I added another cable to allow the P25 sync cable to attach to(From a bad flash extension cable), as I also have a H-5 that I use too. I opened up the HX702 this am to look things over and verified the operation voltages for the microprocessor in the HX702. It appears to be a direct link to the Mamiya back for power, with the Plus going to the inside pin (pin towards the center of the adapter to wards the image sensor opening), and the ground (negative) connection going to the pin nearer the outside edge of the HX702. I examined the circuit and found a capacitor marked with a plus (+) sign next to one side, and verified the other side as connecting directly to the chassis ground - hence the "negative" pin Mentioned above. The positive pins' circuit path goes through a couple of active components that would lead to the belief there is some "active" voltage regulation that occurs on the circuit board. It appears that a small 6 volt battery would fulfill the power requirements of the circuitry of the adapter, and not over-power the microprocessor. I haven't gone further yet, except to measure the physical clearance between the back and the HX702.(0.025 inch). Very small wires would be required for a carefully soldered connection to an external housing for a battery. Since the p25+ in a mamiya 645 mount is stated as communicating with the camera microprocessor through the horizontal pin group, the SHOULD BE no worries of power being in-approprietly applied to the back, but I don't know if I trust that "SHOULD BE" until I do a live voltage test on the adapter with-out the back attached. I have the lab equipment to regulate the voltage and current to determined levels, and will do that as time permits, but will continue to use the HX702 as a "Dumb" adapter (non-powered) that rotates on the rb67 for now. Does anyone else have any further info? Manufactuers don't want to talk to me at all, and it's nice to have a rotating back adapter even if I blow the circuitry in the adapter. Since the Digital backs pins are contacting the adapters' circuity wether the back is powered or not, and I'm getting good images with the unit as a "dumb" 2-shot adapter. I'll go that far. We'll se what I find out. (I've been "figuring things out" since the 60's) (and into photography since the late 70's)