1.    The weight indicator: it is set on the arm lever close to the driving room of the tower crane which  changes with the elevation of the arm, reflecting the angle of the arm on the ground, know the elevation of the arm at different positions, according to the performance table and performance curve of the crane, we can know the amplitude value, lifting weight, lifting height and other reference values at a certain elevation.

2.       Upper limit: it is a safety device installed on the pulley group at the end of the arm to limit the lifting height of the hook head and prevent over-winch accidents. It ensures that when the hook is lifted to the limit position, it can automatically send an alarm signal or cut off the power source to stop the lifting to prevent over-winding.

3.       Torque limiter: it will automatically stop lifting when the load moment reaches the rated load and send alarm signal.

4.        Anti-boom back-up device and anti-back bracket: it is a safety device that will not be lifted when the boom is lifted to the maximum rated elevation angle. It prevents the boom from leaning back when the elevation angle is too large.