PURPOSE: To perform almost the same power supply at the normal operation mode even when an abnormality occurs in a power synthesizer.

CONSTITUTION: In the case of an emergent operation mode where the normal operation can not be performed due to an abnormality in a power synthesizer 3, coaxial switching devices 5-9 are switched from the normal operation mode to the emergent operation mode. The output power from two broadcasting devices 1 and 2 are outputted through terminals T1 and T4 of the coaxial switching devices 5 and 6 to the coaxial switching devices 8 and 9, then outputted through the terminals T1 and T4 of the coaxial switching devices 8 and 9 to the output terminal side of a power distrubutor 4. The power distributor 4 synthesizes the output power from the two broadcasting devices 1 and 2. The output powere synthesized by the power distributor 4 are outputted through the terminals T2 and T3 of the coaxial switching device 7 to the coaxial switching device 10, and then outputted to the coaxial switching device 8 through the terminals T4 and T3 of the coaxial switching device 10, and fed to an antenna 13 through the terminals T3 and T2 of the coaxial switching device 8.