Power supplies for the receiving station are critical. Each box circuit or coded radio receiver in the receiving station has to be served by power that is arrangedTo make it convenient for the receiving station, NFPA 72 allows the choice between three power supply arrangements.   in one of three ways.
Form 4A Form 4B Form 4C Forms 4A and 4B allow the system load to be distributed between two or more common rectifiers and batteries. In any arrangement, the secondary power supply has to be able to carry the entire load of all connected circuits without overloading any of the secondary power suppliesIf a circuit develops a ground, or is crossed electrically with another circuit, each circuit has to be able to supplied by an independent secondary power supply, capable of supplying power to the extent required by the type of power supplied stipulated by the form..

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