A system for the exchange of messages among a multiplicity of processing units includes a data channel and a service line interconnecting respective interfaces of these units. Each interface includes a busy-state detector determining during a test phase of a recurrent time slot whether the service line...http://www.google.com.tw/patents/US4470110?utm_source=gb-gplus-share專利 US4470110 - System for distributed priority arbitration among several processing units competing for access to a common data channel
