PURPOSE: To transmit information in a wide range, by using a signal adopting an ultrasonic wave as a carrier, and utilizing a liquid transmporting pipe laid for the original using purpose.

CONSTITUTION: A water supply main pile 1, water supply branch pipes 2 water supply pipes 3 are filled with service water. An ultrasonic signal transmitted from a transmitter/receiver 7 is transmitted in the water supply pipes through a signal coupler 9 and received by a main receiving device 6. The main receiving device discriminates a called signal, and in case of a terminal to be accessed, starts a main transmitting device 5. The main transmitting device 5 groups the outputs of water meters 4 provided with transmission parts respectively and transmits the grouped output in the water supply pipes 3. A signal from the device 5 is received and demodulated by a receiver 7e of the transmitting/receiving device 7 and tabled in a collecting device 8.