| 摘要 |
PURPOSE:To improve the communication efficiency by constituting a communication system only of data terminal devices of a digital line exchange network (DTE), attaining a long range communication by a 4-wire private line and a short range communication by a digital line taking the line characteristic into account. CONSTITUTION:In processing calling at an interface device 10, a calling request signal is transmitted to a DIF (data terminal device interface) control section 11 from the DTE. When it is given to a main control section 16, the main control section 16 transmits the signal to an NCU (network control unit) 15, checks the presence of collision of calls and when no collision exists, the possibility of selecting signal receiving is informed to the DTE via a DIF control setion 11. Then, the DTE transmits the selecting signal and it is fed to the main control section 16 via the DIF control section 11. Then, the main control section 16 transmits it to the NCU control section 15, the NCU control section 15 starts the NCU 14 and the selecting signal is transmitted from the NCU14 to a line 14a. When a response signal is returned from an opposite party in response to the selecting signal, the NCU14 receives it, the NCU control section 15 confirms this receiving and informs it to the main control section 16. |
