Abstract: The escapement (1) arranged between a motor gear train and a roller (2) to which is attached a sprung balance of a timekeeper, the balance being able to describe an arc of free oscillation and to receive oscillation maintaining impulses, this escapement including first (3) and second (4) toothed wheels meshing with each other, one of these wheels being driven by the motor gear train and a rocking member (5) having: first (41) and second (42) contact means able to receive impulses generated alternately by the first (3) and second (4) wheels, impulse means (11, 12) capable of co-operating with the roller (2) to transmit said impulses to said roller to drive it in rotation and to maintain the oscillations of the balance, and first (43) and second (44) blocking means for alternately blocking said first (3) and second (4) wheels after each impulse transmitted by said impulse means to said roller, said first and second contact means and said first and second blocking means being arranged at the periphery of the