JPS57103447A - Fm transmission system with low power consumption - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a repeating station, by changing the upper band of an FDM multiplex telephony to the lower band to lower the transmission output of the intermediate repeating station when the reduction of the number of used channels is detected as the result of monitoring the number of used channels and a used band. CONSTITUTION:When the number of channels is reduced at night or the like in the FDMFM multiplex telephony signal transmission line, the reduction of the number of channels is detected by a channel number and service band monitoring equipment 23 in the receiving side. The monitoring equipment 23 outputs a channel changes controlling signal (a) and a transmitter output switching control signal (b) and uses a line of the opposite direction to transmit them to a channel switching FDM signal generator 12 of the transmission side and an FDM signal demodulator 21 of the receiving side, and bands of all used channels are changed to the lower band of the FDM signal. Simultaneously, the signal (b) is transmitted to an intermediate repeating station; and in the repeating station, the power source of a high output power amplifier 18 is cut off by the signal (b), and a changeover switch 17 is driven, and the output of a low output power transmitter 16 is connected to an antenna 24 and is transmitted. Thus, the power consumption of the repeating station is reduced without degradation of S/N.