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Nothing so complicated as that. He just uses a switchbox on the surface with one switch per motor. (See step 9) Another way to do it is shown on the home brew ROV website http://www.homebuiltrovs.com/seafox.htmlwhere it shows how to use some old video game joy sticks. I made a Seafox a number of years ago and added a cheapie B&W video camera. I built the whole thing for under $100. See pic.
Electric Ice Scooter