A bi-directional spring clutch having a cylindrical input element mounted on a cylindrical output element, with a wrap spring disposed between them. A control element, in the form of a cylinder, is rotatably mounted on the input element for assuming one of three discrete positions relative to the input element. A key on the control element extends through a window of the input element and is disposed between the ends of the wrap spring. When the control element is in either of its extreme positions, turning of the input element controls tightening of the spring and the transmission of torque, the direction of torque transmission depending upon the position of the control element. Rotation of the input element in the opposite direction results in the key unwrapping the spring so that there is not torque transmission. When the control element is in its middle position, the key bears against neither end of the spring, and torque is transmitted in both directions of rotation of the input element.