To reduce power consumption in transmitting data such as meter- reading through radio communication between a transmitter and a receiver and to prevent malfunction or communication interruption due to insufficient capacity of a battery, for example.

A receiver 11 is connected through a cable to a tapped water meter 10, and a transmitter 13 is connected through a cable to a counter 12. These receiver 11 and transmitter 13 are respectively provided with control parts having a clock. The transmitter 13 transmits a signal at each prescribed time, and during a fixed time before and after that prescribed time, on the other hand, the receiver 11 is turned into a reception state with an intermittent supply of power.