A system for training welders that includes a data generating component, a data capturing component and a data processing and visualization component. In one embodiment, a dental milling system includes a milling tool for milling a dental prosthetic and a spindle operable to receive, fixedly engage, and rotate the milling tool. The detection signal generation circuit generates a stress detection signal based on the first voltage and a second voltage during a test mode. Preventing pieces bulge from widthwise edges of the tongue. Virtual circuits included in the circuit bundle can have different destinations, and include at least multipoint virtual circuits.