detection of an undesired movement characteristic of the platform 100 this undesired movement characteristic may be predetermined based on any number of criteria such as excessive movement speed of the platform 100 when it is being raised or lowered by the hoists 105 or the detection of an obstruction or hazard around the apparatus the user panel 120 contains a number of switches gauges and indicators to allow a user to independently control and monitor each or all of the hoists 105 as well as to monitor the relative depth of the platform 100 as measured and communicated by depth sensor 125 the user panel 120 is connected to the control unit 115 which receives commands and input from the user panel 120 to relay to the power unit 110 the control unit has mechanical electrical or electromechanical components capable of controlling i the starting and stopping of each of the individual hoists 105 ii the speed at which each of the individual hoists 105 are actuated such that the platform 100 is movable at a nominal speed of about one foot per minute iii additional air powered shut off devices located in the apparatus capable of arresting the action of an individual hoist 105 platform 100 or both when the platform is positioned at a predetermined point such as near the very top of its range of motion near the top or coping of the swimming pool or near the very bottom of its range of motion near the floor of the swimming pool 0022 fig2 illustrates the apparatus 10 as installed in a swimming pool of characteristic size and shape in addition to the platform 100 fig2 shows the layout and positioning of a number of elements incorporated into the.