Abstract: A control system for controlling the initiation of detonation of a series of explosive charges (13) spaced apart from each other in boreholes (12) formed in a rock medium (10) to be blasted, said system being operative to apply controlled time difference in the time interval between successive detonations of at least one phase of the series of charges, and which includes at least three successive detonations, so as to reduce the probability of consecutive stimulation and amplification of ground vibration by reason of the detonation of the charges in the rock medium.

Abstract: The invention relates to an electrical distribution system for energizing a plurality of electric circuits in accordance with a predetermined delay pattern. The system as described comprises a control unit, a plurality of circuit delay arrangements each associated with an electrical circuit individual thereto and each circuit delay arrangement is identifiable by a circuit code individual thereto and includes a pulse counting arrangement. The control unit is arranged to transmit the circuit codes to the circuit delay arrangements and the pulse count individual to each circuit code, and each circuit delay arrangement identified by its circuit code is arranged to store the pulse count individual to that code. On receipt of a start signal from the control unit, transmitted simultaneously to all the circuit delay arrangements, each circuit delay arrangement starts its respective pulse counting arrangement and energizes its respective electrical circuit when the pulse count is completed.

Abstract: This invention relates to a detonator firing circuit comprising a control unit and a plurality of detonator circuits. The detonator circuits are arranged to simultaneously receive a "fire" signal and the fire signal initiates all the delay arrangements to allow different groups of detonators to detonate at different times in accordance with a predetermined firing program. In the present invention each detonator circuit has a code individual thereto and the control unit can control and transmit information to every detonator circuit, including the delay to be imparted to the detonator circuit. The identification code for each detonator circuit is preferably one of a large number of identification codes so that the likelihood of the two detonator circuits having the same identification code and having the same firing circuit is extremely small.