There are so many kinds, in total there are two main kinds, which are used widely. One is single line, another is double line. Single line has one pressure port with some exits, but double line has two pressure ports with some exits. Double line could be able to work, in the condition of two pressure ports have pressure. So in the exit of the pump must have reversing valve. While, oil distributor ,also know as divisor, is used to distribute lubricating grease in the lubrication systems.