Detonator roll call

1. A method of conducting a roll call of a plurality of detonators ( 12 ) which includes the steps of:

1. providing a respective roll call counter ( 36 ) for each detonator ( 12 );

2. assigning to each detonator a respective roll call identifier ( 34 ) which is unique to the detonator ( 12 );

3. generating a command which contains a start signal ( 44 ), and at least one parameter, which specifies a detonator status;

4. transmitting the command ( 44 ) to all of the detonators ( 12 );

5. at each detonator ( 12 ), in response to reception of the start signal ( 44 ), setting the respective roll call counter ( 36 ) to a respective first specific value ( 49 );

6. polling the detonators ( 12 ) by transmitting an enquiry signal ( 50 ), by reversal of a voltage applied or transmitted to the detonators ( 12 ), to all the detonators; and

7. at each detonator ( 12 ):

a) in response to reception of the enquiry signal ( 50 ), changing the respective first specific value ( 49 ) in the roll call counter ( 36 ) to a respective second specific value ( 54 );

b) comparing ( 58 ) the respective second specific value ( 54 ) to the respective roll call identifier ( 34 ) for the detonator ( 12 ); and

c) if, at least, the comparison in step b) is positive, and if said detonator status prevails at the detonator ( 12 ), causing the detonator to transmit a respective reply signal.

2. A method according to claim 1 wherein, for each detonator ( 12 ), the first specific value ( 49 ) causes polling to start with a particular detonator ( 12 ).

3. A method according to claim 2 which includes the steps of sequentially transmitting a plurality of said enquiry signals ( 50 ) until each detonator ( 12 ) in the plurality of detonators has been afforded an opportunity of transmitting the respective reply signal.

4. A method according to claim 3 wherein the enquiry signals ( 50 ) are transmitted at regularly spaced time intervals.

5. A method according to claim 4 wherein, for each detonator ( 12 ) the respective reply signal which is transmitted by said detonator ( 12 ) includes information selected from: an identity number for the detonator, the roll call identifier for the detonator, a status signal relating to the detonator, and a check sum for the detonator.

6. A method according to claim 5 which is terminated, after enquiry signal ( 50 ), after a time interval, during which no signal is transmitted which is unambiguously detectable by the detonators despite the detonators not including calibrated timing means, or by transmitting a control signal which is distinct from the enquiry signal.

7. A method according to claim 6 which is implemented in respect of a subset of the detonators in said plurality of detonators by including in the start signal ( 44 ) the respective first specific value ( 49 ) which identifies a starting detonator in the subset.

8. A method according to claim 3 wherein, for each detonator ( 12 ) the respective reply signal which is transmitted by said detonator ( 12 ) includes information selected from: an identity number for the detonator, the roll call identifier for the detonator, a status signal relating to the detonator, and a check sum for the detonator.

9. A method according to claim 3 which is terminated, after said enquiry signal ( 50 ), after a time interval, during which no signal is transmitted which is unambiguously detectable by the detonators despite the detonators not including calibrated timing means, or by transmitting a control signal which is distinct from the enquiry signal.

10. A method according to claim 3 which is implemented in respect of a subset of the detonators in said plurality of detonators by including in the start signal ( 44 ) the respective first specific value ( 49 ) which identifies a starting detonator in the subset.

11. A method according to claim 2 wherein, for each detonator ( 12 ) the respective reply signal which is transmitted by said detonator ( 12 ) includes information selected from: an identity number for the detonator, the roll call identifier for the detonator, a status signal relating to the detonator, and a check sum for the detonator.

12. A method according to claim 3 which is terminated, after said enquiry signal ( 50 ), after a time interval, during which no signal is transmitted which is unambiguously detectable by the detonators despite the detonators not including calibrated timing means, or by transmitting a control signal which is distinct from the enquiry signal.

13. A method according to claim 4 which is implemented in respect of a subset of the detonators in said plurality of detonators by including in the start signal ( 44 ) the respective first specific value ( 49 ) which identifies a starting detonator in each subset.

14. A method according to claim 1 which includes the steps of sequentially transmitting a plurality of said enquiry signals ( 50 ) until each detonator ( 12 ) in the plurality of detonators has been afforded an opportunity of transmitting the respective reply signal.

15. A method according to claim 14 wherein the enquiry signals ( 50 ) are transmitted at regularly spaced time intervals.

16. A method according to claim 1 wherein, for each detonator ( 12 ) the respective reply signal which is transmitted by said detonator ( 12 ) includes information selected from: an identity number for the detonator, the roll call identifier for the detonator, a status signal relating to the detonator, and a check sum for the detonator.

17. A method according to claim 1 which is terminated, after said enquiry signal ( 50 ), after a time interval, during which no signal is transmitted which is unambiguously detectable by the detonators despite the detonators not including calibrated timing means, or by transmitting a control signal which is distinct from the enquiry signal.

18. A method according to claim 1 which is implemented in respect of a subset of the detonators in said plurality of detonators by including in the start signal ( 44 ) the respective first specific value ( 49 ) which identifies a starting detonator in each subset.