| 摘要 |
PROBLEM TO BE SOLVED: To effectively issue an alarm in voice for the user of a portable telephone in a use prohibited zone by detecting the strength of radio wave received by an antenna, comparing it with a reference value and generating sounds for alarm. SOLUTION: When an antenna 1 and a speaker 10 are installed in a hospital and the portable telephone is used in the hospital, for example, its transmitted radio wave is received by the antenna 1. Only the radio wave passed through a band-pass filter 3 inside a receiver 2 is converted to an IF frequency by a mixer circuit 4 and converted into a signal voltage proportional to the electric field strength of received radio wave by a detector 6. At a controller 7, this voltage is compared with a prescribed voltage Vi set to a comparator 8. When it is judged the radio wave received by the antenna 1 has strength higher than a fixed level, a voice generating circuit 9 is operated by the output of a comparator 8 and the prescribed voice is synthesized and announced through the speaker 10 inside the hospital as a voice for alarm. |
