| 摘要 |
A circuit for preventing a radio telephone engaged in a call from being cut off when a power failure occurs, wherein the radio telephone is branched with a wire telephone by a telephone line. When the power is off while engaged in a call, the telephone line is held on by a state of a line voltage and a music on hold is generated. If power turns on again in a holding state, a power off cancel data is transmitted to a portable device. If a response data from the portable device is received, the holding state of the telephone line is canceled and the music on hold is stopped, and the call through the radio telephone is connected again. If the power is not on again or if the response data is not received, it is checked during a given time whether the wire telephone is hooked off or not. If the wire telephone is hooked off or if the given time has passed, the holding state of the telephone line is canceled and the music on hold is stopped. Therefore, the telephone call is continued even when a power failure occurs on an engaged state in the call.
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