My radar detector uses a power cord with a landline phone plug. I had some old wiring and hooked 2 of the wires to the terminals of a new BMW accessory plug. Works fine. Also found out the accessory socket on the dash is hot at all times. If I knew how, I'd wire it to the ignition switch, instead of having to unplug the RD every time I get off the cycle.
4/7 update. Apparently my plug receptacle has been replaced. There are only 2 wires attached to the terminals--both black. Have not tested which is power vs. ground but that is easy to do. The wiring diagram I have points to 4 wires connected to the accessory plugs. Both accessory receptacles are on the same fuse circuit so both are hot with ignition switched off. Typically when I park the cycle I pull the radar detector and lock it up or carry it with me, depending on time/place, etc. I'll just have to remember to unplug the detector when I arrive home .