An automatic call distributor (10) with a multichannel communication bus, a plurality of bus maintenance units (13, 15), and at least one status and control circuit (11) for preventing erroneous resetting of a bus maintenance unit (13) by a status and control circuit (11)....http://www.google.es/patents/US5270699?utm_source=gb-gplus-sharePatente US5270699 - Fault tolerant signaling
