means enabling automatic locking of the canvas soon as the gearing down area has been passed application_number US 201615003886 A description with reference to fig2 illustrating an exploded perspective view of a first belay descender d 1 according to the invention the fixed flange 13 for fitting the rotary cam 10 and the operating lever 11 in the form of a handle articulated on the cam 10 by the pivot pin 14 can be seen the cam 10 and operating lever 11 are arranged on each side of the flange 13 the bearing pin 15 of the device of fig1 of the prior art is replaced by a drive rod 20 and the direct stop 16 is not provided and is replaced by a guide ramp 21 located along the edge of the flange 13 the rod 20 is articulated on the lever 11 by means of a pivot pin 22 and is kept in position by a spring not shown the flange 13 is provided with a recess 23 allowing passage of the rod 20 when if moves along the guide ramp 21 after actuation of the lever 11 in the unlocking direction the recess 23 is delineated at its top part by the guide ramp 21 the cam 10 comprises a first aperture 24 for passage of the pivot pin 12 fixed in a hole 26 of the flange 13 and a second aperture 25 for fixing the pivot pin 14 of the operating lever 11 a second flange 27 is arranged opposite the first flange 13 and collaborates with a spacer 28 to keep the rope in place the second flange 21 can.