A device, supplied to F.S. personnel, that is used for blocking a switch in its normal position, disconnecting it electrically from the A.C.E.I. The device lever, normally in the “open” position, can be moved to the “blocked” position after having received the consent of the A.C.E.I. by means of the internal electromagnet; this consent allows the lever to exceed the intermediate “A.C.” (awaiting consent) position.
With the lever set in a vertical position, the Yale key can be removed, thus blocking the lever and preventing the switch from being moved by the A.C.E.I. The affected switch can be moved by the A.C.E.I. only after the key has been reinserted and the lever turned to the “open” position. With the lever in the “A.C.” or “open” position, the key remains locked in the device.
It is supplied in a watertight case (made of aluminium or fibreglass) mounted on a special stand and set according to the given station protection signals.