/community-hubs/deltav-community-connect/b/safety-weblog/posts/safety-instrumented-system-architecture-160-diagnosticsThe language of process safety is filled with its own jargon. Architectures are described as 1oo1, 1oo2, 2oo2, 2oo3, etc. The “oo” means “out of”. So, 1oo1 means one-out-of-one. William M. Goble and Harry Cheddie wrote a book, Safety Instrumented Systemsen-USTelligent Community 13