| 摘要 |
A gateway apparatus 6 in a TETRA mobile communication system can send and receive call traffic and SDS messages via radio signals with the fixed radio infrastructure 1 on the one hand, and can send and receive call traffic and SDS messages via radio signals with one or more direct mode operating terminals 7 and 8, etc., on the other hand. The gateway apparatus 6 is also configured to be operable such that it does not always relay calls and SDS messages originating from the direct mode terminals 7, 8, etc., to the fixed radio infrastructure 1. This provides a method of allowing a group of direct mode operating terminals to communicate with each other in isolation from the fixed, V+D network 1, whilst remaining able to be reached by users on the V+D network 1 for incoming calls when necessary. |
