S.R. Heavy Equipment manufactures Tower Cranes Automatic Safe Load Indicator. It is a device which is cranes to alert the operator if the lift is exceeding the safe operating range of the machinery.  A Safe Load Indicator (SLI) or an Automatic Safe Load Indicator (ASLI) is a device which is installed on mobile or portal cranes to alert the operator if the lift is exceeding the safe operating range of the machinery.