This device separates the voice portion of the DSL Internet line from the portion that will carry the DSL Internet data. A POTS splitter is also known as a low-pass/high-pass filter. The customer premise splitter allows two wires to activate phone jacks and the other two to activate data jacks. The splitter at the central office allows for separate POTS (Plain Old Telephone Service) and DSL Internet signals, which go to the PSTN (Public Service Telephone Network) and the DSLAM (Digital Subscriber Loop Access Multiplexer), respectively. Both splitters must be present and compatible to allow for simultaneous voice and data transmission.