An isolation member (34) for use in a non-electric detonator cap (10) has an interior passageway (40) extending therethrough and defining a positioning region (44) and a discharge port (56). Positioning region (44) provides a series of interior shoulders (46, 48) and an entry shoulder (52) respectively sized to receive and seat therein signal transmission lines of different outside diameters, thereby longitudinally orienting and spacing the signal-emitting end (30a) from the receptor charge (14). The isolation member (34) is preferably made of a semi-conductive material to bleed off to the shell (12) any static electricity charges transmitted through the signal transmission line (shock tube 30) so as to prevent static discharge initiation of the receptor charge (14).