Subsurface signal transmitting apparatus

This invention relates to a subsurface signal transmitting apparatus of the type for sensing certain conditions in a bore hole and then transferring them to a surface located receiver. A subsurface signal transmitting apparatus including an insulation coupler, a carrier device for mounting the telemetry instrumentation, and a by-pass system for avoiding pressure build-up either above or below the apparatus. The insulation coupler includes a housing member having a central opening defined by an interior surface extending in the longitudinal direction and a mandrel member having an exterior surface spaced from the interior surface of the housing member to provide a gap or clearance with an insulating bonding material occupying the clearance. The surfaces are oriented so that when the coupling is in tension at least a portion of the two surfaces experience interacting forces towards each other in the longitudinal direction of the coupling and in event of failure of the bonding material, the mandrel member is unable to withdraw from the housing member. The by-pass system includes a by-pass tube which extends through central openings of the insulation coupler and carrier device and provides for electrically insulating one end of the assembly from the other but allows for pressure equalization via a fluid passageway. The carrier device has a cylindrical body forming external channels for concealing instruments about is circumference.