| 摘要 |
PURPOSE:To make it possible to reduce an intraoffice transmission loss by improving line balance with a two-wire circuit by selecting a balancing network suitable for a subscriber's line by a four-wire telephone switchboard and then by connecting this network to a two-wire/four-wire converting circuit. CONSTITUTION:Once a subscriber places telephone set 1 in the calling state, exchange 13 detects that by a calling detector that is not shown in the figure and operates line concentrator 17 to select disengaged subscriber's circuit 15. Then, circuit 15 feeds electric current to telephone set 1 by way of subscriber's line 2 and the value of the fed current is detected in circuit 15, etc., to select BN4 suitable for line 2 through balancing network BN selection controller 19, thereby connecting it to two-wire/four-wire converting circuit 3. Consequently, while line balance with the two-wire circuit is improved, the reflux of a calling current can be reduced to lessen the intraoffice tansmission loss of four-wire telephone set 11. |
