A catheter guidance system comprising: (i) a signal generator having a connector, (ii) a wire assembly comprising at its distal and spirals or coils forming a magnetic field generator, (iii) at least one elongated electrical conductor (202, 204) in the wire assembly coupling the connector to the magnetic field generator, the elongated electrical conductor (202, 204) having a diameter, and (iv) a tubing assembly, said tubing assembly comprising: a tubular insulator having a first end connected to the connector, a second end, an internal diameter and an external diameter, the internal diameter being substantially equal to or greater than the diameter of the elongated electrical conductor (202, 204), the tubular insulator being secured to the wire assembly; a union device having a first end and a second end, the first and second ends (116, 118) each having an internal diameter and an external diameter, the first end of the union device being coupled to the second end of the tubular insulator, the internal diameter of said first end being substantially equal to or larger than the external diameter of the second end of the tubular insulator; a fastener securing the tubular insulator to a user-selectable location on the union device; a tubular connector having a plurality of ends, a first one of the ends being attached to the second end of the union device; a catheter having a first end and a second end, said first end being attached to a second one of the ends of the tubular connector; and an end member attached to the second end of the catheter, characterized in that the union device includes a position controller in form of an elongated neck positioned between the first and second ends (116, 118) of the union device, and a stop preventing the distal end of the tubular insulator from passing through the distal end of the union device. (i) a signal generator having a connector, (ii) a wire assembly comprising at its distal and spirals or coils forming a magnetic field generator, (iii) at least one elongated electrical conductor (202, 204) in the wire assembly coupling the connector to the magnetic field generator, the elongated electrical conductor (202, 204) having a diameter, and (iv) a tubing assembly, said tubing assembly comprising: a tubular insulator having a first end connected to the connector, a second end, an internal diameter and an external diameter, the internal diameter being substantially equal to or greater than the diameter of the elongated electrical conductor (202, 204), the tubular insulator being secured to the wire assembly; a union device having a first end and a second end, the first and second ends (116, 118) each having an internal diameter and an external diameter, the first end of the union device being coupled to the second end of the tubular insulator, the internal diameter of said first end being substantially equal to or larger than the external diameter of the second end of the tubular insulator; a fastener securing the tubular insulator to a user-selectable location on the union device; a tubular connector having a plurality of ends, a first one of the ends being attached to the second end of the union device; a catheter having a first end and a second end, said first end being attached to a second one of the ends of the tubular connector; and an end member attached to the second end of the catheter, a tubular insulator having a first end connected to the connector, a second end, an internal diameter and an external diameter, the internal diameter being substantially equal to or greater than the diameter of the elongated electrical conductor (202, 204), the tubular insulator being secured to the wire assembly; a union device having a first end and a second end, the first and second ends (116, 118) each having an internal diameter and an external diameter, the first end of the union device being coupled to the second end of the tubular insulator, the internal diameter of said first end being substantially equal to or larger than the external diameter of the second end of the tubular insulator; a fastener securing the tubular insulator to a user-selectable location on the union device; a tubular connector having a plurality of ends, a first one of the ends being attached to the second end of the union device; a catheter having a first end and a second end, said first end being attached to a second one of the ends of the tubular connector; and an end member attached to the second end of the catheter,