The Schneider Electric LA9FJ4H4G is a mechanical interlock from the TeSys F range, designed to prevent simultaneous closure of two contactors in a reversing or two-speed motor starter configuration. It physically blocks the armature of one contactor when the other is engaged, which is the standard method for ensuring power-circuit isolation in direction-change applications.
This interlock mounts in a vertical stack of three contactors. The compatible devices are listed by position: bottom accepts LC1F185 through LC1F225 or CR1F185 in 3- or 4-pole variants; middle accepts LC1F265 through LC1F330 or CR1F265; top accepts LC1F400 in 2-, 3-, or 4-pole or CR1F400 in 3- or 4-pole. The 3-vertical mounting position means the interlock links the three contactors in a column, which is the typical layout for a two-speed Dahlander winding starter with a separate line contactor, or for a reversing starter with a bypass contactor.