| 摘要 |
PURPOSE: A method of preventing surreptitious using a long-distance call is provided to prevent surreptitious using a long-distance call by using a tone generator in a portable unit when controlling using the long-distance call at a main body of a cordless telephone. CONSTITUTION: A method of preventing surreptitious using a long-distance call comprises judging whether a ring is terminated when a call button is pushed(ST21-ST23), opening, if so, all signal lines so that an instant call is possible(ST26,ST27), and releasing, if not, mute to a reception signal line connected to a receiver until a key button is pushed, wherein a transmission signal line transmitted to a telephone line through a microphone is muted(ST24,ST25).
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