| 摘要 |
PURPOSE:To automatically and most suitably select and set a balance circuit network by controlling a selecting circuit based on the DC resistance of a two- wire line and the level of a signal coming from a two-wire terminal. CONSTITUTION:The DC resistance of the two-wire line connected to two-wire input/output terminals 2 and 2' is detected, and the DC resistance value of a fixed circuit connected to a terminal is subtracted to obtain the DC resistance value of the line. Since the transmission pulse signal of the terminal equipment connected to the two-wire line is set to a prescribed level, the pulse signal transmitted from the terminal equipment is received and the signal level is observed by a level detecting circuit 16 to obtain an extent of signal attenuation. If the DC resistance value and the value of the extent of signal attenuation are specified on plane coordinates, the distance is specified correspondingly to each classification of the two-wire line. Thus, a balance circuit network 8 to be connected is selected and set by a selection control circuit 12 based on the specified distance.
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