| 摘要 |
To prevent violent collisions between two travelling cranes which are movable by electric motor in such a way that they can be switched over from a high to a low speed, an electromagnetically operable control switch (1.1; 1.2) is allocated to each travelling crane. In addition, a sliding control line (3) is provided which has two conductor pairs (4, 5 and 6, 7) which are interrupted at points (b) situated at uniform distances (a) from one another, but in each conductor pair a section of one conductor is connected to the other conductor at its next section in front in the direction of approach. These conductors are tapped by additional sliding contact means additionally provided on one or the other travelling crane, so that, when the travelling cranes approach over a certain distance, the energising circuits of the control switches are completed so that the switching to low travelling speed is effected. <IMAGE>
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