A jet mill includes plural nozzle devices for discharging a composite stream of high velocity fluid. Arc-shaped projections on the front face of a finned heat sink are in heat-conducting relationship with printed conductors on the rear face of the circuit board, which partially surround one lead of each light-emitting diode. In addition, the method includes simultaneously providing a plurality of visual indications. The ESD-protection structure includes adjacent alternating P+ and N+ diffusions located substantially under a bond pad to be ESD protected.