 Telephone companies typically do not allow client-owned equipment to be directly connected to party lines, posing an additional obstacle to their use for data.Telephone service for dispatchers and service personnel between way stations along railways used a form of party line service for many decades starting in the early 1900s.Railroad telephone systems often consisted of several dozen way stations interconnected with a shared line that used DC voltages as high as 400 V for selective signaling to alert called stations.