A method of generating a confirmation time break value in a seismic blasting system, the method comprising: applying a voltage from a seismic blasting machine across a pair of wires connected to a seismic detonator; providing a firing command or a firing signal from the seismic blasting machine to the seismic detonator; sensing at least one electrical parameter while maintaining the applied voltage from the seismic blasting machine across the pair of wires for a non-zero predetermined time (TMAX) after provision of the firing command or the firing signal; determining whether the sensed electrical parameter indicates a successful detonation of an explosive charge associated with the seismic detonator; and if the sensed electrical parameter indicates a successful detonation, using the seismic blasting machine, selectively identifying a confirmation time break value representing a time when the sensed electrical parameter indicates a successful detonation of the explosive charge; wherein: the sensed electrical parameter is a reflected signal generated by reflection from a microwave reflector impedance of the seismic detonator of a signal provided by an RF signal generator within an external sensor interface circuit, said circuit connected via leg wires to an external sensor of the seismic blasting machine, wherein the external sensor interface circuit is configured to monitor the reflected signal at the leg wires, and wherein determining whether the sensed electrical parameter indicates a successful detonation comprises determining whether the reflected signal ceases to be received by the seismic blasting machine within the non-zero predetermined time (TMAX) after provision of the firing command or the firing signal. applying a voltage from a seismic blasting machine across a pair of wires connected to a seismic detonator; providing a firing command or a firing signal from the seismic blasting machine to the seismic detonator; sensing at least one electrical parameter while maintaining the applied voltage from the seismic blasting machine across the pair of wires for a non-zero predetermined time (TMAX) after provision of the firing command or the firing signal; determining whether the sensed electrical parameter indicates a successful detonation of an explosive charge associated with the seismic detonator; and if the sensed electrical parameter indicates a successful detonation, using the seismic blasting machine, selectively identifying a confirmation time break value representing a time when the sensed electrical parameter indicates a successful detonation of the explosive charge; wherein: the sensed electrical parameter is a reflected signal generated by reflection from a microwave reflector impedance of the seismic detonator of a signal provided by an RF signal generator within an external sensor interface circuit, said circuit connected via leg wires to an external sensor of the seismic blasting machine, wherein the external sensor interface circuit is configured to monitor the reflected signal at the leg wires, and wherein determining whether the sensed electrical parameter indicates a successful detonation comprises determining whether the reflected signal ceases to be received by the seismic blasting machine within the non-zero predetermined time (TMAX) after provision of the firing command or the firing signal. the sensed electrical parameter is a reflected signal generated by reflection from a microwave reflector impedance of the seismic detonator of a signal provided by an RF signal generator within an external sensor interface circuit, said circuit connected via leg wires to an external sensor of the seismic blasting machine, wherein the external sensor interface circuit is configured to monitor the reflected signal at the leg wires, and wherein determining whether the sensed electrical parameter indicates a successful detonation comprises determining whether the reflected signal ceases to be received by the seismic blasting machine within the non-zero predetermined time (TMAX) after provision of the firing command or the firing signal.