Telemetry system for drill bore holes

摘要: Apparatus and method for signaling within a drill bore hole without disturbing an ongoing drilling operation. Repeater stations are utilized at intervals along string with the repeater input output being in different noninterfering first second modes. Furthermore, means shown causing successive transmitters of any given mode to produce only negative feedback hence cause overall system be self-stabilizing. Special also selectively attenuating one or both modes transmission between thereby substantially eliminating undesired cases where self-stabilization cannot guaranteed. Both active passive attenuators discussed as well two exemplary systems. One uses electric current magnetic flux other while utilizes signal frequencies