An architecture of so-called system “2 on 2 processors” fault tolerant, in specific railway applications, including two processing units, Normal and hot Reserve, with a Watchdog fail safe; As soon as this “sees” a difference between the two processors of units Normal, excludes this, and the system switches under the control of the unit Reserve, continuing the service. Each unit has two microcomputers and related Watchdog fail-safe, various memory cards and I / O and other duplicate components
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