| 摘要 |
PURPOSE:To operate a main facsimile equipment side stably by holding a telephone circuit changed over to the main equipment side until the facsimile equipment stops operation, by outputting a detection signal when a tone signal for facsimile calling appears on the telephone circuit. CONSTITUTION:Circuit connection terminals 1a and 1b are connected to the primary side of a pickup transformer 21 via capacitors 8a and 8b. The secondary-side output of the transformer 21 is supplied to an amplitude-limiting amplifying circut 22, which holds the level of the signal constant; and a filter 23 extracts only a tone signal and a detecting circuit 24 detects the envelope of the signal. The detection output of the tone signal is spplied from the circuit 24 to a gate circuit 25, and a hook-off signal F is applied from a hook-off detecting circuit 28 to the circuit to control the opening and closure of the circuit 25. During the operation of a facsimile equipment 5, the circuit 25 is closed by a tansmission control signal C or a signal F to intercept a signal from the circuit 24 to a time constant circuit 26, and a telephone circuit is changed over to the equipment 5 side, operating equipment 5 stably. |
