MTS Model FlexTest SE - Manual (Page 222)

Models FlexTest® IIm/GT/SE Controller Hardware
Multiple Controller Connections
FlexTest SE Controller Connections 222
Interlock function Power must be applied to all controllers in the chain for proper interlock
operation. If power is not applied to any one of the controllers, you will not be
able to clear an interlock condition in any of the controllers.
Also, if a cable becomes disconnected from a dependent controller’s Box In
connector, or if a cable is inadvertently connected to the Box In connector on the
master controller, an interlock is set which cannot be reset until all controllers are
restarted.