I use a Resperonics System One Auto. Got the 12v adapter cord from cpap.com. You will be asked for a copy of your prescription to purchase from most C-Pap product retailers. I e-mailed a copy to them.
When I had my sleep study and failed it the place that did it wanted to furnish the machine. I had been warned that would happen and I just politely asked for a copy of my prescription and I would take care of aquiring what I needed. No argument.
The 12v cord comes with a power plug (Cigarette Lighter)on it. I found a always hot 12v wire under the bed and connected a socket I installed on the side of our bed frame to it. I added a heated hose from cpap.com and spliced it into the power wire for the machine. No more rain out from the hose.
Jim