Abstract: An explosive device receives signals specifying a unique communications address for use in a blasting circuit and a required blasting delay. The device has an electric igniter, but no independent power source which might cause accidental detonation. In an address and delay setting mode, when the device is being handled by a blaster, a unipolar signal is transmitted to the device to charge only a control power supply for general communications. In a blasting mode, a bipolar signal is transmitted to charge both control and igniter power supplies. A security code must, however, be transmitted to enable charging of the igniter power supply. Prior to detonation, each explosive device in a blasting circuit responds to a calibration signal by generating a timing circuit test count. A blasting machine processes nominal delays and test counts, and transmits adjusted delays to synchronize operation.