Digital switching systems reliability.- the tropico approach and field results

TROPICOR System is a stored program control (SPC) digital telephone exchange developed by TELEBRAS R&D Center in Brazil. Its major feature is a fully decentralized control architecture based on a microprocessor network interconnected via triplicated signalling bus. Traditional SPC telephone equipment provides centralized, though sometimes distributed, control architecture based on a duplicated central processor. This paper introduces the TROPICO System and respective arquitecture, lighting its differences as compared to centralized systems and discussing the main advantages of its approach. The discussion is backed by pratical field data collected from a sample of 68.8 years of commercial exchange operation.