| 摘要 |
<p>PURPOSE:To minimize the leakage to a 4-wire transmission line from a 4-wire reception line by providing a 2/4-wire conversion characteristic simulating circuit not giving effect on a telephone line and a selection circuit so as to select automatically an optimum network from balance networks thereby switching the balance network of a 2/4-wire converting circuit. CONSTITUTION:The 2/4-wire converting characteristic simulating circuit 31 consists of an adder circuit 23 and a subtraction circuit 24, and a terminal balance return loss is obtained, when impedance circuits 171, 172,...17n of the balance network 14 are selected respectively from the simulating circuit 31. A selection circuit 32 compares all terminal balance return losses of the balance network 14 obtained by the simulating circuit 31, selects an optimum impedance circuit to switch the balance network 14. That is, the optimum balance network 14 is selected automatically and switched depending on the impedance Z0 connected to the 2-wire by adding the simulating circuit 31 and the selection circuit 32 to 2/4- wire converting circuit 30.</p> |
