The communication device has a coupling arrangement with at least a number N of active line assemblies, which are respectively connected to a transmission line and, together with an additional standby line assembly, form a 1:N redundancy group. It is possible to realize traveling of the vehicle with excellent fuel consumption without degrading the overall energy regeneration amount when the vehicle stops. The plug assembly fitted in the fitting part is fixed within the grip housing by an elastic ring and a pressure ring fitted in the expanded portion.