A power system for supplying power to emergency notification circuits (16a-n), the power system comprising: a plurality of primary power supplies (12a-n) connected in parallel and configured to provide a combined current to the one or more emergency notification circuits (16a-n); wherein each of the plurality of primary power supplies (12a-n) is configured to regulate an output current to approximately equal a highest output current provided by one of the plurality of primary power supplies (12a-n); a load-sharing bus configured to provide each primary power supply (12a-n) with a voltage proportional to the highest current provided by any of the primary power supplies (12a-n); wherein each of the plurality of primary power supplies (12a-n) includes a load-sharing controller configured to produce a reference voltage representative of the output current of the respective primary power supply (12a-n); and a load-sharing output path comprising a diode and connected to the load-sharing bus; wherein each load-sharing controller is configured to determine the highest output current by diode OR'ing all of the reference voltages produced by the load-sharing controllers, such that each load-sharing controller is configured to communicate the reference voltage onto the load-sharing bus only if the reference voltage is higher than the reference voltage that is already on the load-sharing bus to ensure that the load-sharing bus always contains the reference voltage of the primary power supply (12a-12n) that is producing the greatest output current; characterized in that the power system further comprises one or more emergency notification circuits (16a-n) for powering emergency notification devices (22a-22n,) and a single backup power source configured to provide power when one or more of the primary power supplies (12a-n) become unavailable, each of the plurality of primary power supplies (12a-n) includes a boost regulator circuit for boosting a voltage of the single backup power source; wherein each boost regulator circuit is configured to provide as an output: the voltage of the single backup power source when the voltage of the single backup power source is above a specified voltage; or a boosted voltage when the voltage of the single backup power source is below the specified voltage. a plurality of primary power supplies (12a-n) connected in parallel and configured to provide a combined current to the one or more emergency notification circuits (16a-n); wherein each of the plurality of primary power supplies (12a-n) is configured to regulate an output current to approximately equal a highest output current provided by one of the plurality of primary power supplies (12a-n); a load-sharing bus configured to provide each primary power supply (12a-n) with a voltage proportional to the highest current provided by any of the primary power supplies (12a-n); wherein each of the plurality of primary power supplies (12a-n) includes a load-sharing controller configured to produce a reference voltage representative of the output current of the respective primary power supply (12a-n); and a load-sharing output path comprising a diode and connected to the load-sharing bus; wherein each load-sharing controller is configured to determine the highest output current by diode OR'ing all of the reference voltages produced by the load-sharing controllers, such that each load-sharing controller is configured to communicate the reference voltage onto the load-sharing bus only if the reference voltage is higher than the reference voltage that is already on the load-sharing bus to ensure that the load-sharing bus always contains the reference voltage of the primary power supply (12a-12n) that is producing the greatest output current; characterized in that the power system further comprises one or more emergency notification circuits (16a-n) for powering emergency notification devices (22a-22n,) and a single backup power source configured to provide power when one or more of the primary power supplies (12a-n) become unavailable, each of the plurality of primary power supplies (12a-n) includes a boost regulator circuit for boosting a voltage of the single backup power source; wherein each boost regulator circuit is configured to provide as an output: the voltage of the single backup power source when the voltage of the single backup power source is above a specified voltage; or a boosted voltage when the voltage of the single backup power source is below the specified voltage. the voltage of the single backup power source when the voltage of the single backup power source is above a specified voltage; or a boosted voltage when the voltage of the single backup power source is below the specified voltage.