Voice and Radio Signals
When voice signals take over
Radio and voice communication is used when the operator cannot see hand signals - blind lifts, long booms, walls, or a signalperson who must reposition out of sight. OSHA (1926.1420) treats radio, telephone, and other electronic signal transmission as a signal system in its own right: it must be tested before use, must not create a hazard, and must stay clear and reliable for the duration of the lift. The vocabulary matters more than the hardware. A good voice command names the function first, the direction second, and the amount third: “Hoist, three feet.” “Boom up, slow.” “Swing left, stop.”
Traps
- Ambiguous words. “Up,” “down,” “in,” “out,” “left,” and “right” mean nothing until the function is named. “Up” could be hoist, boom up, or extend. Questions reward the answer that specifies the function.
- Who is in charge. Only one person directs a given crane at a time. Do not relay commands through a third party; the operator should know which voice is authorized.
- Lost communication. If the radio fails, the message is garbled, or contact breaks, the operator stops and holds the load until communication is restored. The signalperson does not guess.
- Stop is universal. A stop or emergency stop call must be obeyed regardless of who transmits it, and it should be unmistakable - say “EMERGENCY STOP” plainly rather than “whoa” or “hold on.”
Worked example and rule of thumb
Two cranes are setting a beam and the signalperson on the far side keys the radio and says “swing right.” Correct response: identify the crane and the function (“Crane 2, swing right, slow, two feet”), get confirmation from that operator, and keep the channel clear of unrelated traffic. Rule of thumb: function, direction, amount - and if you cannot say which crane, do not key the mic.