Abstract: A detonator of the type comprising an electrically-fired fusehead in an explosive charge comprises a conditioning means which has two states, normal and armed, and a control means for effecting a change from normal to armed state. The detonator cannot be fired when the conditioning means is in the normal state, and the control means may comprise electronic circuitry for recognizing and acting only on appropriate control signals. Accidental and unauthorized firing can thus be eliminated. Other embodiments include an actuator incorporating a delay capable of remote precise calibration and a safety device for reducing still further any risks involved when using these detonators in blasting operations. The detonator is preferably in modular form wherein the coupling together of the detonator, actuator, power unit, etc. forms the necessary electrical connections.