| 摘要 |
PURPOSE:To increase anti-crosstalk and anti-noise performance of an amplifying type telephone set, by supplying a DC current to a transmitter and receiver in a handset, without increasing the number of cores of a connecting cord. CONSTITUTION:A receiver 4 and a transmitter 5 are provided in a handset 1 and they are connected with a 4-cored connecting cord 3 and an amplifying type telephone set main body 2. The power supply to a transmission amplifier 7 is made with one core of the cord 3 from the power supply V3 of the main body 2 and two cores of the receiver 4. The audio signal from the transmitter 5 is amplified at an amplifier 7 and transmitted to an audio signal transmission and reception circuit 8. An audio signal SIG received from a transmission line is amplified at a reception amplifier 6 and transmitted to the receiver 4. A bridge circuit is formed with phase inversion resistors R1, R2 of the main body 2 and voltage dividing resistors R3, R4 of the handset 1, and when adjustment is made without call reception component at a point (c), the crosstalk from the reception to transmission system can be avoided. |
