DA560: Three door normally closed interlock The DA560 monitors the state of 3 doors. This 12VDC powered unit is microprocessor controlled for greater functionality. The unit can be supplied with optional sets of changeover contacts for timer alarm and violate outputs. The timer alarm contacts change over if a door, having been opened, is not closed in a predetermined time. The time is user selectable (see example). The violate contacts change over if more than one door is open at a time (e.g. if a closed door is forced while the other door is open).