The Dynamometer fitted to these machines is of Single Sheave Type. It may be mounted at the boom head or on the pulley mast of the crane. The Dynamometer is of mechanical design concept with electrical equipment restricted to one transducer and one switch.  Variations in the transducer output signal caused by a change in line pull in the live end passing back to the drum caused by the sheave friction and rope bending losses is automatically compensated for in the system.  Many indicators do not incorporate this correction. Such indicators accept that the Dynamometer gives different signals for the same load on the hook, dependent on whether the load is being hoisted or lowered in conditions of operation, which may require the crane to derrick out and lower off simultaneously. The effect of any such inaccuracy on multifall reeving is such as to permit the crane to be operated beyond safe working radius without any alarm signal. Wylie SLI systems incorporate a patented feature that ensures that the Dynamometer signal will be constant regardless of motion of the hoist line.