| 摘要 |
A transmission input/output device for signal transmission through a telephone line, with reduced power consumption, size, and cost. The device includes: a resistor (1), connected to the telephone line, for setting a signal input and output impedance; and a transmission control circuit (3) for amplifying the transmission signals to be outputted to the telephone line, including: a variable resistor (11), connected in series with the resistor (1), for supplying voltages corresponding to the transmission signals to be outputted to the telephone line into the resistor according to changes of an impedance of the variable resistor (11); and an operational amplifier (21) for controlling the changes of the impedance of the variable resistor (11) by supplying an output according to the transmission signals to be outputted to the variable resistor. <IMAGE> |
