This describes a method for improved data signaling equipment for use with well-drilling tools for rapidly sending measurements made down the hole in the wellbore to the surface without the need of an electric cable. A special well tool is connected into a drill string having a drill bit coupled thereto...http://www.google.com.au/patents/US3964556?utm_source=gb-gplus-sharePatent US3964556 - Downhole signaling system
