Re: Separate Control
Contacts are usually called wet or dry when you are talking about two separate pieces of equipment. Consider an elevator control panel and a fire alarm control panel. The fire alarm panel has a contact to shut down the elevator. The elevator panel has an input to shut it down that consists of two terminals.
The contact in the FACP panel would be a dry contact if both its terminals are not connected to anything. It could be a relay contact for example. The FACP can engage the relay and close the contacts, but the contacts aren't connected to anything else in the fire alarm control panel.
For this dry contact to be used by the elevator panel, the elevator panel would have to put a voltage on one of its input terminals. When the FACP contact closes, the voltage appears at the other elevator panel input terminal.
For a wet contact, the FACP would apply power to one side of the contact. Then the input to the elevator panels may be another relay that engages when the FACP contact closes.
Thats not as clear as I hoped when I started, but I hope that helps.
Steve