| 摘要 |
PURPOSE:To attain incoming call notice such as emergency communication without excessively modifying conventional constitution by allowing a packet exchange network to use a logical channel number ''0'' reserved between said network and each data terminal device to supply notice to an emergency incoming call to a data terminal device. CONSTITUTION:When a call request will emergency display exists from an LCN=2 logical channel in a data terminal device 2B to a data terminal device 2C, it is decided that this call is the call request with emergency display in a call detection processing section 5 of a packet exchange network 1, a table retrieval processing section 6 retrieves the content of a communication state table 3 and it is decided that there is no logical channel not in use except LCN=0 logical channel which is kept to the reserve state at all times relating to a data terminal device 2C. A response processing section 7 makes call rejection to the calling data terminal device 2B in response to the said busy state. On the other hand, an emergency incoming notice processing section 8 makes emergency incoming notice to the data terminal device 2C via LCN=0 logical channel 11-0 in the data terminal device 2C. |
