Abstract: A signal tube operated switch includes a contact arrangement which is moved from a first, open circuit position to a second, closed circuit position by a shock wave or pressure pulse initiated by a detonator. The switch is preferably an electric switch and in at least one embodiment includes a movable conductive piston consisting of at least one portion in continuous conductive engagement with the conductive signal tube. The other portion of the contact arrangement causes a change in the circuit after the contact arrangement is relocated to the second circuit closing position. Accordingly, the overall working efficiency of delay detonators is improved.