| 摘要 |
In order to either permit communication to continue or to permit a call to be placed while a mobile unit is located in a zone of weak signal strength such as a tunnel or underground parking, a booster is disposed in the zone and arranged to establish communication with the mobile unit over a booster channel. When the mobile unit detects the signal strength being below a level at which communication is possible, the unit switches to the booster channel and establishes temporary communication with the booster. This enables the booster to be conditioned to establish a communication link between the land site and the mobile unit over a voice channel. The mobile unit is responsive to the conditioning of the booster to switch to the voice channel. Hence the need for wholesale relaying of all channels is obviated by the selective relaying which is possible via the provision of the booster channel. |
