At Strathclyde University we have a dual local area network configuration consisting of a commercial Cambridge Ring and an Ethernet-style network called Strathnet designed and built in the Department of Computer Science. The majority of the hosts in our dual configuration are PDP-11 and LSI-11 computers. With these networks we are investigating the comparative performances of each and investigating the architectures and protocols of local networks in general. One of our chief interests is in designing "access units" by means of which computers, terminals and other devices are interfaced to local network communication media. In this paper our dual network configuration is outlined, our approach to building a general-purpose network access unit is explained and a description is given of how we at present interface the PDP-11 and LSI-11 computers to both networks.