| 摘要 |
PROBLEM TO BE SOLVED: To provide a two line/four line conversion circuit capable of realizing echo attenuation of about 40 dB. SOLUTION: In the two line/four line conversion circuit, an echo canceler circuit is arranged on the four line side of a hybrid circuit. On the two line side of the two line/four line conversion circuit, a two winding transformer is arranged for separating the two line side and the hybrid circuit. The two winding transformer has transmission impedance of 600 ohms, and one side open impedance is about 9.6 H or higher, when a signal output level is about 0 dBm at frequency of 300-3,400 Hz, so that the signal output level is a given value which is limited by the desired transmission loss and the profile size of the transformer, or lower in this configuration. COPYRIGHT: (C)2006,JPO&NCIPI
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