| 摘要 |
PURPOSE: To prevent trouble by an electronic tone while securing smooth communication in public facilities requiring quiet environment by selecting automatically a call mode of a portable telephone set by means of a switching signal transmitter installed in public facilities. CONSTITUTION: When a portable telephone set 20 is carried in public facilities, a switching signal from a switching signal transmitter installed in the facilities is received via an antenna 101 and the signal is fed to a BPF 24 via a frequency converter 23 or the like and the switching signal is separated. A level discrimination circuit 25 discriminates a level of the switching signal and when the level is higher than a threshold level set by a setting switch 122, an electronic tone call circuit 124 is replaced with a vibration call circuit 125 automatically via a call mode changeover circuit 26 in a central control circuit 21.
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