Abstract: A pressure impulse for initiating a pressure-impulse initiatable fuse is generated by an electric discharge created in a spark gap between electrodes of mutually opposite polarity. There are used electrodes which are movable relative to one another and voltage is applied to the electrodes when the distance between the electrodes is too great for an electric discharge to take place therebetween, whereafter the electrodes are caused to approach each other at least until a discharge occurs.

Abstract: An electric detonator cap has a casing, which accommodates an explosive detonator charge, an electrically ignitable means for firing the detonator charge, a chargeable and dischargeable electric energy source for igniting the firing means, and an electric circuit arrangement, including a controllable switch means connected between the energy source and the firing means, an electric delay circuit, and a decoder. The energy source is connectable via connecting wires extending out from the casing, to an electric current source for charging the energy source, and the decoder is electrically connectable to said connecting wires and is adapted upon receipt of a specific electric firing command signal supplied through said connecting wires to actuate the delay circuit in a manner to close the switch means after a predetermined delay time.