Single push-piece chronograph

A chronograph including a chronograph train, means for coupling said train and a device for controlling the coupling means, which includes:

• a shuttle pivotably mounted about an axis, a first angular sector of which is provided with two notches defining first and second stable angular positions, and a second angular sector of which includes cut out portions,
• an elastic member cooperating with said notches to keep the shuttle in one of said stable positions, and
• a push-piece cooperating with said cut out portions to pivot the shuttle, as a result of a first application of pressure, from the first stable position to the second stable position, and as a result of a second application of pressure, from the second stable position to a third intermediate angular position,
• wherein said third intermediate position is unstable and defined on said first angular sector of the shuttle by an inclined surface located between said notches, said inclined surface being arranged such that the action of the elastic member causes the shuttle to pivot from said third position to said first stable position when the push-piece is released, and wherein the device for controlling the coupling means further includes means for locking the shuttle in the third unstable position when the push-piece is pushed in.