Use this tag for questions relating to a special class of servos which have continuous 360 degree motion both clockwise and anticlockwise.
Wikipedia describes Continuous-rotation servos as servos that do not have a limited travel angle, instead they can rotate continuously. They can be thought of as a motor and gearbox with servo input controls. In such servos the input pulse results in a rotational speed, and the typical 1.5 ms center value is the stop position. A smaller value should turn the servo clockwise and a higher one counterclockwise.