The invention concerns a data transmission technique for real-time applications and non real-time applications in a communication network comprising several nodes connected by communication channels. The control unit 60 sets a of registration set value A1 for determining a color registration error suppression level and a dropout set value. A plurality of tubes are fixed to the support and extend away from the end of the dielectric, with the fibers positioned within the tubes. The controller oscillates a secondary oil pressure, estimates the belt slip condition by monitoring a phase difference between oscillation components, and reduces an actual secondary oil pressure to maintain a predetermined belt slip condition. Installation formations may be provided on or in the head portion to facilitate installation of the bushing in a hole in the wall.