The invention relates to NPN and PNP bipolar transistors and to a method for the production thereof, said transistors being characterised by a particularly high collector-emitter and collector-base blocking voltage. The master node is configured to communicate with a number of nodes and allocate bandwidth therebetween by sending outgoing signals and receiving incoming signals over a transmission medium. The disclosure includes further embodiments wherein lines of weakness are introduced into the flanges of zippers in reclosable packages or bags. The valve prevents the backflow of blood from the coronary artery into the heart chamber. A hole for passing a light beam emitted from an optical writing unit toward the image carrier therethrough is formed in part of the case bottom wall of the process cartridge higher in level than part of the case bottom wall below the cleaning blade.