A fail safe detector will output “detect” when the loop circuit is failed. On the free exit loop this will keep the gate open until the situation is fixed. This is useful in applications where it is important to allow traffic flow to continue. A fail secure detector will never output “detect” when the loop circuit is failed. This will keep the gate closed. This is useful in high-security areas or installations where containment is needed. The DML-9LP is a fail secure detector. Note: Never use a fail secure detector on a safety loop.