Arrangements and associated methods are described for providing an isolated electrically conductive path in a system in which a boring tool is moved through the ground in a region. The system includes a drill rig and a drill string which is connected between a boring tool, or other in-ground device,...http://www.google.fr/patents/US6223826?utm_source=gb-gplus-shareBrevet US6223826 - Auto-extending/retracting electrically isolated conductors in a segmented drill string
Auto-extending/retracting electrically isolated conductors in a segmented ...
