To automate channel level adjustment in installation, extension, and maintenance inspection of a relay amplifier consisting of a master unit that is placed in a dead-band zone of a mobile phone system and makes transmission reception with a radio base station and of slave units that are connected to the master unit with an optical cable and distributingly placed to form zones for a mobile unit so as to enhance the work efficiency.
The master unit 3 is provided with a MODEM 35, a control circuit 36, and a changeover device 37 that selects a control operation to an operation mode or a maintenance mode, and each slave unit 4 is provided with a MODEM 46 and a control circuit 47. When the changeover device 37 is set to the maintenance mode, an alarm reporting is turned off, the master unit 3 receives reception signal level data of the master unit and each slave unit via the MODEM 35 according to a channel adjustment program stored in the control circuit 36 and automatically controls gains of variable gain amplifiers 8, 44 so as to compensate a loss in response to the length of an optical cable 5.
SHIMADA NOBUYASU
KAGAYA NORIYUKI
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