In order to provide an annular combustion chamber which can be heated without thermal distortion, expands without distortion, and is reliably closed, and for repairs can be opened and permanently closed again and can be reconditioned, the inner andor outer shell of an annular combustion chamber is produced from a rotationally symmetrical sheet metal. The nesting block performs positioning of the workpiece by being brought into contact with the root portion of the hemming flange portion with which the workpiece is formed. In this regard, the aim is to cause the laser source to melt down or explode and, in connection with this, to initiate the explosive. Thus, in addition to the transmission of direct-current power, information can be transmitted only by the connection of two positive and negative terminals. Telephones may, for instance, be the only equipment required by the entities.