Patent ID: 7649474

Claim:
A drill string communication system for communicating information along a drill string between a boring tool and a boring machine, the system comprising: an insulator assembly adapted to provide an electrically insulated gap between a drill string communication path and a soil engaging electrode; a transmitter assembly comprising: a data transmitter assembly adapted to encode and transmit a data signal; and a signal coupler adapted to provide a controlled electrical connection between the drill string communication path and the soil engaging electrode, the signal coupler comprising: a transformer having a primary winding and a secondary winding; and a current regulating circuit adapted to adjust a voltage across the primary winding to maintain a substantially constant current amplitude in the primary winding; wherein a first side of the secondary winding is connected to the drill string communication path and a second side of the secondary winding is connected to the soil engaging electrode; and a receiver assembly comprising: a toroidal pickup coil having an annulus and positioned such that the drill string communication path passes through the annulus, the pickup coil adapted to produce a signal voltage in response to a signal current on the drill string communication path; and a signal processing assembly adapted to process the signal voltage from the toroidal pickup coil and to extract the data signal.