Abstract: An optical unit of plastic provided with a surface for incident light and a surface for outgoing light, wherein the surface for incident light is designed to face a light source and the surface for outgoing light is designed to face an element for receiving light so as to optically connect the light source and the element for receiving light and wherein the optical unit is so shaped that light that comes from the light source and is incident on the surface for incident light forms a first image of the light source within the optical unit and a second image of the light source after having gone through the surface for outgoing light and the optical unit is provided with an attenuating portion for attenuating the quantity of light passing therethrough in the vicinity of the position where the first image is formed.

Abstract: A LAN interconnection apparatus is coupled through a first port to an ISDN and through a second port to a local area network (LAN). Through the ISDN, the apparatus is connected to a remote LAN or an ISDN user. A network address and a host address of an internetwork (such as the Internet) as well as a telephone number of the ISDN are used to uniquely identify remote LANs and ISDN users. A database is provided for associating network addresses with port numbers of the apparatus and associating host addresses with telephone numbers. Upon receipt of a call indication, the apparatus stores a source telephone number contained in the call indication into a lookup table. In response to a packet from the LAN, a port number and a telephone number are detected in the database using a network address and a host address contained in the packet, respectively, as keys.