Sun Microsystems Inc, Mountain View, California, and five other computer companies are to enter the token ring market, having signed agreements with Willemijn Holding BV, Rotterdam, Netherlands, owner of Soderblom token ring patents. They join more than 30 other previously licensed token ring producers. However, long-term token ring user Apollo Computer Inc of Chelmsford, Massachusetts has refused to pay for a licence and has been sued by Willemijn for infringement of the Soderblom patents in the US. The five additional licences have gone to Massachusetts-based companies Fibronics International Inc of Hyannis and Stratus Computer Inc of Marlboro, McData Corp of Broomfield, Colorado, and Californians Racore Corp of Los Gatos and Netronix of Petaluma. The Open Token Foundation, formed last month by 3Com Corp, Santa Clara, and Madge Networks Ltd, London, is attempting to bring producers and users of token ring products together to ensure interportability. Texas Instuments, Memorex Telex, National Semiconductor Corp and Western Digital are amongst those who are supporting the foundation, whilst Sun, which demonstrated a token ring product at Comdex in November, says it is actively monitoring the situation, with a view to joining.