 With party-line service, particularly if there were more than two subscribers on the line, it was often necessary to complete a long-distance call through the operator to identify and correctly bill the calling party.In some cases, the calling party would misidentify themselves in an attempt to send the bill to another party.A two-party line split between "tip party" and "ring party" could be created in such a way as to allow the central office to determine which party placed an outbound toll call by detecting that one of the ringers was disconnected when that subscriber went off-hook.