Detonator construction

A detonator which includes a tubular casing with a closed end and an open end, a base charge inside the casing adjacent an inner surface of the closed end, an electronic module which is located inside the casing, the electronic module including a body of a plastics material, an electronic circuit which comprises a substrate and electronic components, at least a part of the electronic circuit which includes the electronic components being embedded in the plastics body with a portion of the substrate projecting from the body, the body including a first end from which said portion of the substrate projects and a second end which opposes the base charge, a housing which is mounted to the projecting portion of the substrate and which is spaced from the first end of the body, the housing including a passage which extends through the housing from an inlet to an outlet, a sensing structure mounted to the substrate opposing the outlet from the housing, a plug which is located at least partly in the open end of the casing and which is sealingly engaged with the casing, and a shock tube with an end which is secured to the plug and which opposes the inlet to the housing thereby to direct a shock tube event emitted at the end of the shock tube upon ignition of the shock tube, through the passage onto the sensing structure.