| 摘要 |
The single transformer generally used in a duplex coupler for coupling local telecommunication equipment, such as a modem, to a telephone line may be replaced by a number of transformers or other suitable forms of DC isolation device which then enables each transformer and its associated circuit network to be specifically tailored to optimize the operation of the coupler system. The transmit output path 3 is connected to a transformer 2 having a center-tapped secondary winding 11 which is connected across the communication line 4. A second transformer 5 has its primary winding connected between the center-tap and the line 4, and its secondary winding coupled to the receive input 6. By optimizing each transformer the intermodulation products and other unwanted products are reduced. The coupler system may be miniaturized and the line matching components incorporated in or selected by a specific line cord designed to match the network characteristics.
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