| 摘要 |
In a two-way communications system involving portable-mobile-base station transmission, a priortization method prevents interference caused by more than one mobile repeater at a single location relaying simultaneously, or by a lowband transmission skipping in from another location. When a repeater enters the system at a location, it monitors the base and portable channels, and if there is transmission activity on either channel it goes to a non-priority state. If there is no activity, a silent carrier burst is momentarily transmitted on the base channel, then the repeater goes to a non-priority state. Unless a repeater at the scene is in the priority state, each other mobile unit, upon detecting the burst, begins to repeat it out on the portable channel. When interrupted by its interrupt clock, the repeater listens for a short interval on the portable channel and if any transmission is heard, remains inhibited or in "receive" mode. The last mobile repeater to be interrupted will, of course, hear no other transmission and will return to "transmit". This unit will be established as the only unit in the priority state at that location. Any portable channel transmission will prevent base channel transmission from being repeated out on the portable channel, thus a portable-to-portable or portable-to-base transmission will have priority over base-to-portable or "skipped-in" transmission. When the unit in priority leaves or switches channels it is removed from the priority state and transmits a momentary silent carrier burst so that a new priority unit is established as before. |
