PURPOSE: To enable plural data gathering devices, installed on a transmission line in the two-way CATV system, to use the same carrier as the carrier that a central controller uses for polling, to perform polling by being actuated by data gathering devices.

CONSTITUTION: A data gathering device 6 sends a polling actuation signal, including a storage part specification number, back to the central controller 2. The central controller 2 having received this signal performs two-way polling to subscriber terminal devices 5.1-5.m on a specified storage part by using the same f0 and f1 as the normal polling carrier. Data which are gathered are stored in the storage part. After the polling, the central controller 2 sends out the contents of the storage part to the data gathering devices 6 at a time with the carrier f0.