JPS54130821A - Line concentrator of analogue line - Google Patents

Abstract

PURPOSE:To prevent S/N of output signals from deteriorating more than S/N of each input circuit by providing a circuit which detects whether analogue signals are present or not and a gate circuit which controls each input circuit on a basis of the detection result of the circuit above and combining the output of gate circuits. CONSTITUTION:Input lines I1 to In are connected to branch circuits H, and one output of branch circuits H is connected to gate circuits G respectively, and the other is connected to detector circuits D which detect whether analogue signals over a fixed level are present or not. The output of detector circuits D is connected to gate circuits G, and input signals of gate circuits G are connected or disconnected by the output of detector circuits D. Then, respective outputs of gate circuits G are inputted to synthesizing circuit C, and all input signals are combined and outputted at one output terminal O. By this constitution, noise of input circuits where analogue signals over a fixed level are absent is eliminated, and S/N of combined output signals can be improved.