Electrical medical equipment that includes a user operable primary adjustment mechanism containing two or fewer user-adjustable elements, and a controller adapted to control and alter at least one output parameter of the equipment, the controller connected and responding to input from said primary adjustment mechanism to alter said output parameter, the primary adjustment mechanism having at least four conditions a first condition which the mechanism returns to without user input, a second condition, following manipulation of one of the elements from a first condition, a third condition, following manipulation of one of the elements from a first condition, and a fourth condition following manipulation of the same element manipulated to achieve the third condition to another position, wherein in each condition, the mechanism provides a distinct output as input to the controller, which responds to the input by: maintaining the output parameter at a previous level while the input indicates the mechanism is in the first condition, incrementing or gradually increasing the prevailing level of the output parameter while the input indicates the mechanism is in the second condition, decrementing or gradually decreasing the prevailing level of the output parameter while the input indicates the mechanism is in the third condition, and setting the level of the output parameter to zero when the input indicates the mechanism is in the fourth condition.
