This invention relates to sequential blasting utilizing electronic circuitry to steer detonating pulses to successive detonators. Modules are provided which contain a two-terminal element that has the characteristic that in its first normal state it has a high resistance in at least one direction and it may be changed into a second state in which it has a low resistance in both directions by a suitable pulse. Further, a detonating signal does not flow from one power line to the other through the particular module that is being addressed, but from one side of one module through a connecting link and then through the other module. Thus, each module has an input steering terminal and an output steering terminal, with the output steering terminal of each module connected to the input steering terminal of the next module. Then, in use, current flows from one power line to a power terminal of one module, through its output steering terminal to the input terminal of the next module, through that module and to the other power line. Thus, with each detonating pulse, a detonator is fused and one of the elements passes into its second conducting state. As the detonator goes into a non-conducting configuration the next pulse is steered via the element that is now conducting to the next module.