A communication system includes a communication unit with a first part and a number of a second part, where the second part is arranged to be placed at the location of an end user, and where the first part is common for a number of second parts. The flow-inverting device allows the blood flow within the filtering unit to be kept unchanged even following an inverted circulation in the patient-side artery and vein branches controlled by the blood pump. The method includes determining an off-normal operating condition of the rotary machine facilitating undesirable contact between the rotatable member and the stationary member, monitoring a parameter associated with the off-normal operating condition, and preventing operation of the rotary machine while the monitored parameter is within a predetermined range. 0 mm, and a thickness of the polypropylene layer is from 25 to 75% of the wall thickness. A distance between ones of the pixel electrodes located adjacent to each other in the column direction is equal to or larger than a line width of the signal lines.