Abstract: Apparatus for timing and initiating a multi-shot blast is disclosed and claimed. The apparatus comprises a programming tool 16 for individually programming a plurality of electronic detonator arrangements 18.1 to 18.5 with delay time data relative to a common initiate command signal. The programmed electronic detonator arrangements 18.1 to 18.5 are all connected to a data communication cable 28 connected to a control unit 20. The control unit transmits the initiate command signal to all the detonator arrangements on the cable 28. Upon reception of the initiate command signal, the detonator arrangements start timing out their respective programmed delay times to cause their associated charges 12.1 to 12.5 to explode at the end of the delay times. The blast may be aborted by a disarm command on the cable 28 at any time before the initiate command signal is transmitted on the cable.