Through the input switch, the +24V DC power is fed to the DC/DC converters that convert the 24VDC power into -48V DC power. All the converter outputs are connected to a DC bus in the DC distribution unit that powers four communication equipments with the -48V DC power from the converts. The three input poles of the input MCCB are connected together. Every output pole of the input MCCB connects to two converters.
The system provides three dry contacts for generating alarm signals that are load disconnection alarm signal, DC/DC converter failure alarm signal and input power failure alarm. Every dry contact is connected to a 2-bit DIP switch. If both bits of the three DIP switches are set to “ON”, these three dry contacts are connected in parallel and become one dry contact that connects to a DB9 connector. This dry contact outputs system failure alarm signal. The dry contacts and the DB9 connector cannot be enabled at the same time.