| 摘要 |
PURPOSE:To improve the fluctuation of level of a voice signal by controlling the output level of an MODEM an impedance and a balancing network by the state information of a terminal device connected to the identical line with the MODEM. CONSTITUTION:An output of the MODEM 1 is supplied to an amplifier 2 via a parallel circuit comprising a resistor R1 and a switch SW1; and the output of the amplifier 2 is connected to an unbalancing/balancing converting circuit 3. Outputs X, Y of the converting circuit 3 is connected respectively to terminals A, B of a telephone line via a parallel circuit comprising a resistor R6 and a switch SW2. A parallel circuit comprising resistors R8, R9 and switches SW4, SW5 is connected between the outputs Y, X of the converting circuit 3 and inputs C, D of a balancing/unbalancing converting circuit 4, and further a switching circuit of balancing networks Z1, Z2 is connected between both the lines. Then each switch is controlled for changeover by a relay 9 connected to a terminal device 8 to change the amplification factor of the MODEM and also change the impedance of the input/output impedances and the balancing network circuits. |
