기기 제어기능에서 다음과같은 내용이 있는데 자세히 무슨 내용인지 모르겠읍니다. 혹시 이런 내용을 이시는 분 있으면 좋은글 부탁합니다.
Each pre-alarm and shutdown point shall have an indication light on the control panel. A local audible horn with visual indication and silence button is required. All the pre-alarm points shall be wired to a single contact for wiring to a common trouble alarm in the main control room. All shutdown switches shall be wired to a second contact for a seperate independent signal to common shutdown alarm. The light shall be designed for "first out" determination.
특히 single contact, second contact, "first out" determination의 의미를 잘 모르겠읍니다.