| 摘要 |
In a radio concentrator system found by a central station (3) and remote stations (4), demand-assigned data channels are constantly monitored to detect when they are congested. When an emergency call is received from a subscriber terminal (6), a dial tone is sent to the terminal if the emergency call occurs simultaneously with the detection of a congestion. On hearing the dial tone, the subscriber dials an emergency destination address, which is received by a remote station and compared with a list of predetermined addresses and verified if it matches one of the predetermined addresses. The dialled information is sent from that station to the central station, where it is relayed to a switched network (1). An emergency channel is established to the network for routing the emergency call. This channel may be permanently provided and demand-assigned in response to an emergency channel assignment request, or first selected by a remote station requesting an emergency call and access is granted by the central station if no collision occurs between competing emergency calls. Alternatively, no emergency channel is provided in the system and one of the data channels is cleared when an emergency call is detected simultaneously with the occurrence of a congestion. The cleared channel is used as an emergency channel to complete the emergency call. |
