| 摘要 |
PROBLEM TO BE SOLVED: To prevent malfunction caused by the response radio wave of portable telephone set owned by the other person even in the environment that a lot of portable telephone sets closely exist. SOLUTION: A band pass filter 3 is provided for passing only the radio waves correspondent by the machine types of main body of telephone set corresponding to the response radio wave received by an antenna 2 of incoming call reporting device 1, and the radio wave of frequency used for its own portable telephone is selected out of various frequencies received at the antenna 2. At the same time, a high frequency amplifier 4 is provided at the output of band pass filter 3 and the response radio wave made different for each machine type is amplified at the suitable amplification factor. Thus, a suitable sensing distance is applied between the portable telephone set and the incoming call reporting device and the device can be prevented from reacting to both the different type of proximate portable telephone set and the same type of distant portable telephone set. |
