The LA9FH4H4F is a mechanical interlock accessory from the TeSys F range, designed to physically prevent two contactors from closing simultaneously. It interlocks bottom-position LC1F115 through LC1F150 3P or 4P contactors (or CR1F150 equivalents) with top- or middle-position LC1F265 through LC1F330 3P or 4P contactors (or CR1F265 equivalents), mounted three vertically.
Mechanical Interlocking — What It Means on the Panel
Mechanical interlocking uses a physical bar or linkage between contactor armatures so that only one can close at a time. This is typical for reversing or star-delta motor starters where simultaneous closure would create a phase-to-phase short.