Patent ID: 8130114

Claim:
An entry detecting system, comprising: a terminal device; a point-to-point communication device; an entry detecting device; and a guard device; wherein the point-to-point communication device includes a transmitting-receiving antenna having directivity in a specific direction and is configured to specify an entry direction of the terminal device; the point-to-point communication device communicates by radio with the terminal device via the transmitting-receiving antenna so as to detect a response time from the terminal device and report detected response time to the entry detecting device; the entry detecting device detects a distance from the point-to-point communication device to the terminal device based on the response time reported by the point-to-point communication device, generates entry detecting information based on the detected distance, and transmits the entry detecting information to the point-to-point communication device and the guard device; the point-to-point communication device transmits the received entry detecting information to the terminal device; the terminal device outputs an alarm in a case where the terminal device receives the entry detecting information from the point-to-point communication device; and the guard device outputs an alarm in a case where the guard device receives the entry detecting information from the entry detecting device, and wherein the entry detecting device transmits the entry detecting information to the terminal device via the point-to-point communication device in a case where the distance from the point-to-point communication device to the terminal device is a first distance; and the entry detecting device transmits the entry detecting information to the guard device in a case where the distance from the point-to-point communication device to the terminal device is a second distance shorter than the first distance.