| 摘要 |
Spectrum efficiency is increased by eliminating the requirement for a base station to transmit signals to maintain synchronization with a handset when there is no call in progress. A base station and an associated handset normally maintain RF silence 504. When a handset wishes to set up a call, it synchronizes to any other traffic 506. The handset then becomes the sync master with respect to its associated base and rings the base which acts as sync slave for initially synchronizing handset and base. Thereafter, the call continues with the base and handset reverting to their normal roles as sync master and slave respectively 512, 514. To set up a call between two handsets independently of the base, an intercom mode is selected (804, Fig. 8), a first handset is established as sync master and the other remains as sync slave (808, 810), with the first handset reverting to sync slave after the end of the call (816). The arrangement may be used in a TDMA/TDD slow frequency hopping spread spectrum communications system. <IMAGE>
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