Apparatus for use in a blasting system

An apparatus for use in a blasting system which includes a spool with a hub, first and second discs which are mounted to the hub, an elongate flexible signal-transmitting conductor which has a first end and a second end and which is coiled on the hub between the discs, at least a first detonator which is connected to the signal-transmitting conductor at or near the first end, a connector device which is connected or exposed to the signal-transmitting conductor at or near the second end, wherein the signal-transmitting conductor includes spaced-apart markings or formations and wherein the spool includes a sensor, responsive to passage of a marking or formation past the sensor to produce a measure of a length of the signal-transmitting conductor which is uncoiled from the hub and a release mechanism which, in use, permits a degree of rotation of the spool or movement of the conductor when a tensile force exerted on the conductor increases above a predetermined level, thereby to reduce the level of the tensile force exerted on the conductor characterised in that the connector device includes, wholly located inside the hub, a transmitter/receiver module, a battery and a processor and, on one of the discs, connector formations which are adapted to establish communication with a control device.