Voting Logic

The architecture or voting arrangment used in the field instrument or final control element of a safety instrumented system (SIS) to reach a certain safety integrity level (SIL). Voting logics include one-out-of-one (1oo1), 1oo2, 2oo2, 2oo3, etc. For example, a 2oo2 voting logic indicates there are two protective devices/instruments in a system and both devices (two-out-of-two) are needed to properly shut down the system or mitigate the hazard. 1oo2 indicates that only one of the devices would be required to properly prevent the situation from occurring.