Bus testing logic is built into some of the devices connected to the bus to enable these devices to perform diagnostic testing of the bus. In order to be able to ensure the horizontal alignment of the platform at all times, an adjustment device 30 is assigned to at least one of the hold-down systems 20 with which the position or engagement depth of the rope 5 in the rope groove 17 achieved with the corresponding hold-down system 20 can be controllably varied. The massage assembly includes a pair of massage members.