Electric detonators consist of aluminum shell, which contains the explosive charge, the delay element and the fuse head. The required electrical energy for the initiation of the detonator, is supplied by two plastic-insulated metal wires called "leg wires".
The explosive charge consists of a base and a primary charge. The delay element contains a pyrotechnical chemical substance that burns with a predetermined speed. By using pyrotechnical substances with different burning speeds, detonators with different delay times are obtained.
The fuse head consists of two metal contact foils, connected on one side by a bridge wire. The other two ends are attached to the leg wires. When sufficient current is passed through the bridge wire, the latter is heated up ang ignites the fuse head. The resultant flame initiates the delay element and the explosive charge. Leg wires are solid conductors of either tinned copper or steel, covered with plastic insulation. The free ends of leg wires are shunted for protection against stray currents. The delay period number of each electric detonator is marked on tag attached to the leg wire.
