Coordinators
Commerical Door Hardware for Fire Rated Double Doors
What a Coordinator does is "coordinates" the sequence of the doors closing.
The Inactive door needs to close first, then the active leaf. Normally used on Double Door openings that are fire rated - due to each leaf is required to be self latching and self closing. Doors with closers on each leaf and/or astragals are prime locations for Coordinators.
See our Blog about the three different kinds of Coordinators