An exhaust gas treatment device for internal combustion engines and the like includes inlet and outlet end caps, two catalyst substrates, and a two-piece housing. The kink may be substantially S-shaped, Z-shaped, U-shaped, wave-shaped or coil-shaped. voltage source, a smoothing circuit, connected to the output of the rectifier circuit, for generating an intermediate circuit voltage, and an inverter fed with the intermediate circuit voltage, at the output of which inverter a connection for the load circuit containing the lamp is connected. The interior surface of the solid wall forming the interior edge of the hole is preferably substantially flat.