The CATV system includes a center device and a plurality of terminal devices. The center device sends downstream timeslots, to the terminal devices, including upstream timeslots occupancy information and collision information. Upstream timeslot occupancy information indicates whether or not an upstream timeslot corresponding to the downstream timeslot is vacant, and collision information indicates whether or not a collision has occurred. The terminal device receives the downstream timeslot, checks upstream timeslot occupancy information to detect upstream timeslot in the vacant state, and sends upstream data to the center device via the vacant upstream timeslot. If the upstream timeslot makes a collision, the center device detects it and sends a downstream timeslot which includes collision information indicative of the occurrence of the collision. The user of the terminal device recognizes the collision having occurred or not by referring to the collision information.