| 摘要 |
PURPOSE:To prevent a side tone amount and a decrease in losses in terms of four-line relay connection by providing a switching circuit for functioning by a switching control signal so as to give simultaneously detour and losses. CONSTITUTION:Resistance values of resistances 41-44 are assumed to be R, R, alphaR and betaR, respectively. When with the aid of the signal of a switching control line 37 an analog switch 45 is in the off-state, detour amount R goes to zero, because the output signal of an amplifier 32 inputted through a connection line 39 will not be propagated to a connection line 40. The output signal of a decoder 55 inputted through a connection line 38 is provisionally doubled by an amplifier 46, however, it is attenuated to 1/2 only by the resistances 41 and 42, and therefore its loss goes to zero at the result. Next, when the analog switch 45 is in the on-state, the output signal of the amplifier 32 inputted through the connection line 39 is attenuated by the resistances 41-44 to be propagated to the connection line 40, and its detour amount goes to beta/(alpha+beta+2alphabeta). In case of the output signal of the decoder 35 inputted through the connection line 38, after it is provisionally doubled by the amplifier 46, it is attenuated by the resistances 41-44 to be propagated to the connection line 40, and its loss goes to 2alphabeta(alpha+beta+2alphabeta). |
