each module starting up the traction module 4 propels the whole of the device along the conduit following the progress of the device being feasible in various ways either by measurement of the length of a tape hooked to the last module and unwound in the course of progress or by seeking through the roadway with the aid of a radiation transmitter and detector when the tool 24 proves to be close to the secondary conduit 12 where the branch is to be restored the traction module 4 is immobilized and is locked against the conduit by control of its radial extensors 40 a television camera 21 equipped with a skimming light illumination device searches for the shadow produced by the concavity 13 caused by the obstructed shunt 12 the searching movements of this camera are monitored by a tv screen 60 situated on the control desk 6 and controlled by the action on the positioning module 3 when the tool 24 is just opposite the shunt to be restored 12 control of the piercing module permits the simultaneous starting up of the rotational movement of the tool as well as its radial advance in case the axis of the tool should not be exactly in the axis of the secondary conduit 12 the flexible coupling device 80 disposed between the positioning module 3 and the piercing module 2 permits slight positioning errors to be absorbed when the plug 14 obstructing the conduit 12 is pierced all the way through the tool advance limit contact 26 controls the reverse rotation of the.