Abstract: In the ISDN system complex line adapting circuits are provided on the two sides of the transmission line and they handle an extensive protocol. These circuits are divided into two sub-circuits connected to one another over fixed interfaces. The sub-circuit which is located nearest to the transmission line, however, is to have a considerably varying structure depending on the transmitting medium. For a modular structure it is now proposed to subdivide this sub-circuit into two partial circuits interconnected over a newly created simple binary interface. Thus, only the partial circuit which is located nearest to the transmission line needs to be specifically designed for the transmitting medium, for example, glass fibre lines, whereas the protocol management is performed in the other partial circuit, which always has the same structure irrespective of the transmitting medium.

Abstract: The invention relates to an arrangement of inspecting light waveguide end faces by observing the interference pattern formed by means of measuring light in the airgap between a plane transparent plate and the end face of a light waveguide abutting on said plate. A less elaborate measuring device requiring less space is obtained in that the measuring light is led towards the end faces to be observed, via the light waveguides (1, 2, 23, 24).