A Load Moment Indicator LMI system operates on the principle of reference/real comparison. The real value, resulting from the pressure measurement and geometric sensors, is compared with the reference data stored in the central processor memory and is evaluated in he microprocessor. An analog indication of % capacity is displayed via an operator’s console. When limits are reached, an overload warning signal is generated. At the same time, the crane movements that increase load moment such as hoist down, telescope out, and boom down will be locked out. The fixed data regarding the crane, such as dimensional data, capacity charts, boom weights, and centers of gravity are stored in memory chips in the central processor unit. This data is the reference information used to calculate the operating conditions. Boom length and boom angle are registered by the length/angle sensor, located inside the cable reel, mounted on the boom. The boom length is measured by the cable reel cable, which also serves as an electrical conductor for the anti-two- block switch. The crane load is measured by pressure transducers attached to the piston and rod side of the lift cylinder. Controls on the operator’s console allow the operator to select the operating mode (main boom, jib, etc.) as well as the parts of the line currently in use. The system will then limit operation to the capacities on the selected load chart, or the maximum permissible line pull in that configuration. After the engine is started and the PTO is engaged, the LMI powers up and conducts an automatic test of the complete system. After two successful system tests without errors, the system is ready for operation. In case of a system error, both the overload and anti-two-block lights on the central unit will illuminate. The interactive user guidance considerably simplifies the input of operating modes as well as the setting of geometry limit values