Objects of the present invention are to provide an integration circuit which produces no integration leak so that the bit accuracy is improved in a sigma-delta modulation circuit or a delta modulator circuit, which is based on a single flux quantum circuit that uses a flux quantum as an information carrier, and to provide a method for reducing thermal noise and quantization noise. The PLL in the receiver includes a filter with an adjustable bandwidth. Finally, catalysts for polyurethane compositions are disclosed which represent coordination compounds between bismuth and at least one aromatic nitrogen compound. The LED-support structure is a heat sink transferring heat from the LED illuminator to the housing.