The Aqua PC uses a special power supply designed for commercial lorries that senses when the ignition switch is turned on/off and then powers up/down the PC. We have used this feature to allow our customers to fit a remote power switch (replicating the switch on the front of the PC) which is useful on a boat when the PC system unit is buried away somewhere safe (but difficult to access).
When 12v is detected on the white wire, the PC will power up, as if you pressed the push switch on the front of the PC. When the 12v is removed from the white wire the PC will start its power down sequence. The power board will keep supplying power to the Aqua PC during the power down cycle but after 2 minutes, the voltage will be cut and the Aqua PC will be in a very low power <5mA state rather than the normal standby state that most normal PCs go to after shut down that continuously consumes 0.15 Amps.
So, to fit a remote power switch simply connect a conventional On/Off switch; either toggle on/off type or a push on/off switch (not momentary type) between the white wire and red wire (boat’s 12v or 24v supply voltage).