Importance

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Abstract

There is disclosed a control circuit for switching between a facsimile unit and an automatic answering telephone unit. A current detecting circuit with satisfactory linearity between the mutually insulated input and output sides is used for detecting a DC current on a communication line, indicating a communication state of the telephone unit and also for detecting an AC signal, representing a speech communication signal and used for recording an incoming message in the automatic answering telephone unit. This structure allows to insulate the recording circuit and the facsimile circuit from the communication line without a transformer, thereby reducing cost and dimension of the apparatus.

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First Claim