There are four wires coming out of the Whelen unit. +12,GND,mode, and sync. You change modes by temporarily connecting the mode wire to +12.

The Whelen strobe modes are basically, 4,3,2, or 1 blinks at a time, or solid. Each mode has two modes one for chaining to other units. I wish that one of the wires would just do solid then it would make a terrific brake light. I've just been using it in the default 4 blinks mode.

I just used some bits of aluminum strip and "P" clamps to attach it to the rear rack. I discarded the mounting stuff it comes with and am just using the unit itself. real simple. I added a molex connector and a 9V battery connector. The battery is just sitting in the rear bag. I have an 8 Cell AA pack ready when the darn 9volt battery runs out. I've got about 10 hours on it now and it's still flashing, Not quite as bright but still brighter then the LD500, and thats with 9V instead of 12. I still don't know what the current drain is as it only gives max current, but it's quite efficient.

The mounting holes are on the two outside edges of the metal back plate about 3 1/2 inches apart, so the vertical unit would need a bit of finagling to fit on the typical verticle reflector mount.

The electronics appear to be potted (although I didn't actually dissasemble it), so I'm not concerned with weather. The unit is designed to be mounted on the ouside of emergency vehicles.

While riding the Apple Cider Century about 6:00 am and very dark and foggy every car that passed moved completely into the opposite lane, well before reaching me, and I had forgotten to remount the reflector so the only rear lighting was the whelen. So it was bright enough to penetrate the ground fog.

I'm still a little concerned that a flashing red light might be restricted to emergency vehicles, but I haven't been stopped yet.