the link module 30 moreover the entry of other substances such as dirt rocks gasses and the like may also be prevented in selected embodiments the link module 30 may include one or several recesses 38 a c to house various components contained by the link module 30 or repeater 30 selected recesses 38 may contain circuitry while others 38 may be used for batteries or other components one or several channels 41 may be milled or formed into the cylindrical housing 34 to provide for the routing of wires between recesses 38 in selected embodiments a connector 40 may be used to connect link module circuity to a cable wire or other link traveling up or down the drill string 14 an aperture 42 may likewise be provided for routing cable wire or other transmission means up or down the drill string 14 referring to fig3 an inverted cross sectional view of the drawing of fig2 is illustrated as illustrated the link module 30 may be characterized by a general wall thickness 48 likewise in regions proximate recesses 38 or other channels 41 a thinner wall thickness 50 may be present nevertheless a critical wall thickness 48 should be maintained to provide structural reliability to the link module 30 to support stresses encountered in a downhole environment the cylindrical housing 34 may be constructed of any suitable material including steel aluminum plastics and the like capable of withstanding the pressures stresses temperatures and abrasive nature of a downhole environment as illustrated one or several transmission paths 42 a 42 b may be milled or formed into the wall of the link module 30 to provide an outlet for cables wires or other transmission media exiting the recess 38 in selected embodiments connector 40 may be provided to simply link.