| 摘要 |
PURPOSE:To allow the method to cope with even the subscriber calling type service by sending an incoming signal from a subscriber, closing a switch when it is detected by an incoming signal detector so as to apply incoming communication. CONSTITUTION:An incoming switch 1 is opened in normal state, terminated by a termination resistor R to suppress flowing of incoming summed noise to the center. In this state, when an incoming signal is sent from the subscriber in case of a telephone call or data communication, an incoming signal is inputted from, e.g., a branch terminal 13i of a tap-off 20, passes through a low pass filter(LPF) 18, reaches an incoming signal detector 2 and the incoming switch is close when the detector 2 discriminates it as 'presence of incoming signal', the incoming signal passes through an LPF 17, a branch circuit 12 and a directional coupler 11 sequentially and sent from the input terminal to the center. Thus, the incoming summed noise is suppressed and the incoming signal is sent at any time even in the communication system of the subscriber call type. |
