The characteristics of the fitting to be welded, such as the fusion time, are registered via a barcode on the fitting. An electrofusion control unit (ECU) supplies the electrical energy necessary to heat the coil. When the coil is energised, the material adjacent to it melts and forms an expanding pool which comes into contact with the surface of the pipe. The continued introduction of heat energy causes the pipe surface to melt and a mixing of pipe melt and fitting melt takes place; this is vital to produce a good weld. Following the termination of the heat cycle, the fitting and the pipe are left to cool and the melted material solidifies to form a sound joint.