COMMUNICATION METHOD/DEVICE

摘要

PROBLEM TO BE SOLVED: To identify the existence of an intruder into a communication link through the use of information communicated with an existing service supply protocol and to provide precise safety in a communication system. SOLUTION: In the system/method for improving the safety of operation, a remote device can identify that there is a difference between a first signal transmitted by a center site and a first signal received by the remote device 104. Thus, derived numbers or numerals having a prescribed relation are used. The derived numbers or numerals are displayed to a user for verifying terms by the user or the derived numbers or numerals can be used in the remote device 104 or the center site 102 for transparent verification. Considrable safety is added without substantially changing a communication protocol.