Volt-free contacts required?可以翻译成“是否要求无电 ...? what does volt free contact mean ? volt-free and dry contact mean the same thing. if a control system supplier offers a dry contact for you to read as a status bit, then he is offering to close a contact (relay or contact output) that is nothing more that a stand-alone set of contacts with no voltage , current, or anything else impressed across the contact set. it becomes the user's responsibility to determine how to sense that contact closure. usually you do this by putting a voltage on one side and sensing the voltage on a return line from the other side of the contact when it closes. once you apply voltage to the contacts, it becomes a wet contact. you "wet" the contact with a sensible voltage level. http:///question/index?qid=20070601040505aac51qb [ ]查看更多