the one which is placed on that part of the user 39 s head 2 opposite the casing 1 the arrangement of the two bands 5 5 u2032 as well as the articulation means 28 are such that in position of non use or folded position the two bands 5 5 u2032 of the receiver are applied against each other in a parallel position as shown in fig1 on the contrary in position of use the sheath 26 may pivot about the rotation element constituted by the screw 7 and the bands 5 and 5 u2032 may be opened out and disposed substantially in line with each other so as to ensure that the receiver is held in position on the user 39 s head 2 as shown in fig9 depending on the measurements of the head the bands 5 and 5 u2032 will be more or less opened out so as to ensure correct hold of the receiver rotation of the bands and of the sheath with respect to the casing about the articulation element 28 will make it possible to adjust the relative angular position existing between them and the part 1 b extending the casing 1 as the user desires the present device is particularly advantageous in that it allows easy rapid and precise adjustment and positioning on the user 39 s head 2 while also allowing it to be easily folded into rest position as shown in fig1 in a particularly advantageous form of embodiment of the invention the receiver will comprise means for angular indexation of the band or of the sheath with respect to the casing 1 to that end as shown in fig1 the rotation element 3 is provided on its periphery with notches 31 which are.