Having worked at Power Tower the whole summer of '99 I might be able to fill you in regarding pt's saftey systems. Each tower has its own allen-bradley control panel/touch screen display unit. Jeff is right with his observations of the electrical contacts. While the car is on the ground the two metal surfaces are in contact with all saftey harnasses. Back in the control tower the ride operator monitors the touch screen-which has a numbered section of the screen for each seat. When a particular seats restraintis open the light on its section of the screen will turn red (and disable the operators ability to launch the ride,) when the seat's restraint is locked the light in its particular section of the screen will turn green. Once the ground crew finishes loading the guests, one pt crew member will hold an enable button while the other will give a thumbs up. If the enable button is pressed and one of the restraints is not completely down, the touch screen will display a large warning screen and will disable the operators power to start the ride cycle. At that time the operator will tell the crew to check a certain restraint. It is basically foolproof.