| 摘要 |
PURPOSE:To minimize a detour signal reaching a 4-wire transmission line from a 4-wire reception lien by providing the 1st coder/decoder (CODEC) applying A/D conversion, the 2nd CODEC having the same filter characteristic, a 2/4-wire converting characteristic simulating circuit simulating a detour signal eliminating characteristic and a selection circuit switching a balance connection network. CONSTITUTION:A 2/4-wire converting characteristic simulating circuit 31 receives a signal from a reception line 41 of a PCM highway, generates simulatingly a detour eliminating signal component caused by an impedance circuit 171 of a balance network 14 of a 2/4-wire converting circuit 30 at first, this signal component is added to a signal of a PCM highway transmission line 42 to calculate a signal detoured to a transmission line 42 from the reception line 41. A selection circuit 32 compares all detour of the 2/4-wire converting circuit 30 switching sequentially the balance network 14 obtained by the 2/4-wire conversion characteristic simulating circuit 31 in this way with the signal characteristic to select the optimum impedance thereby switching the balance network 14. |
