Abstract: An actuator for use in conjunction with a detonator for blasting comprises electronic circuitry which on receiving input signals generates an output arm signal to arm a detonator, and then after a predetermined delay an output actuate signal to fire the detonator and an associated explosive charge. The delay is capable of being remotely and precisely set. The actuator is preferably used in conjunction with a control device which has a microcomputer whose memory contains arm and actuate codes and which has both arm and actuate keys. This microcomputer is such that the actuate keys must be operated within a predetermined period after operation of the arm key, otherwise an actuate signal is not transmitted to the actuator.