Didn't know any of those still existed since they have been out of production for many years now. I love mine, once I rigged up a connection to the serial port in the back to replace the lame connection to the mini port in the front that comes loose with the tiniest amount of pressure on the cord. Basically the unit connects by this cord and requires its own power. Yes you must leave the 996 on for it to work, and the RH96 will not power off the scanner at all. Also, if your scanner is going to be located a distance from the front seat, you would need to wire in an external speaker as well as the RH96 does not come with a speaker.
There was a guy who several years ago put together a connection that linked the two units with a Cat5 cable which was a great idea (wish they were still available). So as it is, with mine, I have two wires running from the scanner (in the rear of the car) to the RH and a separate power connection to the fuse block.