BURIED PIPE MARKING SYSTEM

PURPOSE:To detect the change of pressure in a pipe by generating a high level signal and a low level signal, changed over by the switch of a pressure detector, on the basis of DC power generated by a data communication part. CONSTITUTION:The loop coil 210 of a marking device 200 receives carrier wave from a survey device 100 and sends it to an IC element 230 for a data carrier so as to transmit a modulation signal from the IC element 230. A worker learns from low-level information that the internal pressure of a buried pipe 300 is normal. When the internal pressure of the buried pipe 300 becomes abnormal due to the damage of the buried pipe 300, a pressure detector 240 performs the changeover of a switch so as to make the input terminal of the IC element 230 a high level. The IC element 230 generates the modulation signal including buried information and high level information, and the loop coil 210 transmits the modulation signal from the IC element 23. Since the survey device 100 displays the high level information, the worker learns that abnormality is generated to the buried pipe 300.