Triconex 3501E is TMR Digital Input Module. Each TMR digital input (DI) module has three isolated input channels which independently process all data input to the module. A microprocessor on each channel scans each input point, compiles data, and transmits it to the main processors upon demand. Then input data is voted at the main processors just prior to processing to ensure the highest integrity. All critical signal paths are 100 percent triplicated for guaranteed safety and maximum availability. 

Each channel conditions signals independently and provides optical isolation between the field and the Tricon.All TMR digital input modules sustain complete, ongoing diagnostics for each channel. Failure of any diagnostic on any channel activates the module Fault indicator which in turn activates the chassis alarm signal. The module Fault indicator points to a channel fault, not a module failure.