The LA9FK4G4F is a TeSys F mechanical interlock from Schneider, designed to physically prevent simultaneous closure of two contactors mounted vertically in a three-contactor stack. It interlocks bottom-position LC1F115 through LC1F150 or CR1F150 contactors (3P or 4P), middle-position LC1F185 through LC1F225 or CR1F185 contactors, and top-position LC1F500 (2P, 3P, or 4P) or CR1F500 contactors. Mounting position is three vertical units, which is the standard arrangement for reversing or two-speed motor starters in a TeSys F panel.
The paperwork has to be clean: verify the part matches the interlocked device list before committing the line.
Integration note
This is a purely mechanical accessory — no wiring, no coil, no auxiliary contacts. It clips onto the contactor bodies and uses a sliding bar to enforce the interlock. Verify the contactor frame sizes against the compatibility list; the LA9FK4G4F covers a wide range from LC1F115 up to LC1F500, but the position in the stack (bottom, middle, top) is fixed per the listing.