Abstract: An isolation member (34) for use in a non-electric detonator cap (10) is of substantially cylindrical shape and has an interior passageway (40) extending therethrough and defining a positioning region (44) and a discharge port (56). Positioning region (44) is dimensioned and configured to snugly receive and seat therein a signal transmission line (30) and to orient the signal-emitting end (30a) thereof to aim along the longitudinal axis of cap (10) through a diaphragm (42) at the target provided by receptor charge (14). The isolation member is positioned between, and spaces the signal-emitting end (30a) of the signal transmission line (30) from, the receptor charge (14) contained in the detonator cap. The isolation member comprises grooves (58, 58a, 58b) to provide an alternate flow path through which a signal emitted by the discharge end (30a) of a signal transmission line (30) can reach the receptor charge (14) should the signal fail to burst the diaphragm (42 ).