| 摘要 |
PURPOSE:To realize the supply of the working power source before enclosure of the DC circuit by flowing the current less than the non-operation level of the relay of the exchange when the polarity of the telephone circuit is inverted and thus securing the terminal call detecting action. CONSTITUTION:When the calling is given via the exchange for the data collection, the polarity of the telephone circuit is inverted to make switch circuit 13 conduct. Then the operating current is supplied to call signal detection circuit 15 from auxiliary power circuit 16. In this case, the consumption current is limited to the current less than the non-operation level of the relay which detects the loop current within the exchange, thus avoiding the action for the incoming detection at the exchange side. Then circuit 15 becomes active to detect the call signal transmitted from the exchange side. And then connection circuit 17 is started. Thus the telephone circuit is connected to the data terminal T via circuit 13 and 17 to secure the supply of the fixed current to the data terminal. In this case, for the consumption current, the current over the sensitivity level of the exchange relay is flowed in order to realize the incoming detection at the exchange side. |
