摘要 |
The present invention provides a telephone line automatic switching system which allows a user to selectively use the international telephone communication leased network, the domestic telephone leased network, and the domestic public communication network in a PABXO, a telephone, key phone, a facsimile, etc. This system includes a telephone line selection switch circuit (6), call signal sensing circuits (7), (8), a control circuit (10), a domestic line selection and operation display circuit (11), an international line selection and operation display circuit (12), a terminal operation state detecting circuit (9), line busy circuits (11), (12), a call sensing interruption circuit (15), and a telephone line selection circuit (16).
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