PURPOSE: To extremely narrow an exclussive band width on a circuit by providing low frequency data modulating demodulating parts and RF band converter parts for modulating a signal into an RF band, at a central device and a terminal transmitter.

CONSTITUTION: The modulated signal of the RF band is inputted to the RF band converter part 31 of the terminal transmitter 30 through a two-way CATV circuit network 20, and is demodulated into the frequency modulated signal of low frequency by the RF converter part 31, and further, the frequency modulated signal of low frequency is demodulated into a digital signal by the low frequency data modulating demodulating part 32, and inputted to a meter inspection processing part 33. The meter inspection processing part 33 performs a call address check, and at the time of a coincidence with a self-address, reads the value of an automatic inspection meter 40, and assembles an answering telegram, and outputs it to the low frequency data modulating demodulating part 32. The low frequency data modulating demodulating part 32 converts the answering telegram into the frequency modulated signal of low frequency, and converts it into the RF band by the RF band converter part 31. By converting into the RF band after modulating at the low frequency, the deviation width of a frequency can be made extremely narrow, and the exclussive band can be narrowed.