In CE4, a communication terminal transmits data including a latency_off value “1”. After receiving the data, an environment information measuring apparatus transmits data since a latency counter value is “0”. The latency counter value becomes “2” and a latency_off counter value becomes “1”. In CE5, the communication terminal transmits data including a latency_off value “0”. Since each of the latency counter value and the latency_off counter value is not “0”, the environment information measuring apparatus does not receive the data from the communication terminal. The latency counter value becomes “1” and the latency_off counter value becomes “0”. In CE6, since the latency_off counter value is “0”, the environment information measuring apparatus receives the data from the communication terminal.