Modular Jacks are relatively simple in their construction. In the single port example here, a modular jack has a shield, a housing, terminals, and light pipes. Modular Jacks are passive connectors, so they carry the signal from the Ethernet wire straight through to the PCB without any transformation of the signal. Depending on the application, a discrete magnetic package may be required on the board to filter the signal. If a PoE application is being used, a wider range of components will be needed on the board, including but not limited to a PoE controller chip, bridge rectifiers, and a PoE transformer along with the additional circuitry and isolation components required for PoE.