| 摘要 |
PURPOSE:To prevent the detour of a PB code to a receiver, by performing mutually inversely the switching of a link and a trunk line for the transmission of PB code from an extension telephone set or a link for the transmission of voice signal from a relay line. CONSTITUTION:The 1st link is switched with a central controller CC to transmit a code PB1 from an oscillator. The controller CC controls a digital network DNW so that a path 2 is cut off as shown in T in the timing when the code PB1 is transmitted. Thus, the path 2 is cut off while one output of oscillators OSC1-OSCi is connected to a decoder DEC of a trunk line COT, allowing to avoid the forming of the detour making the output of the oscillator reach the receiver PBREC. |
