I don't know if there is any requirement, just say my own opinion. You are like a freight elevator. Sometimes you are afraid that workers will hit the goods, so you ask the ladder operator. Some communities also have ladder workers, but considering the cost, many communities have been monitored and let the ladder workers go to see the monitoring. Those office buildings, shopping malls and so on are rarely equipped with elevator personnel. These still depend on the meaning of the elevator property owner.