Grandstream Networks GXP280/285 Instruction Manual page 5

NTP Server: Enter [ntp.jst.mfeed.ad.jp].
Disable Call Waiting: Select [Yes] to enable call waiting. Select [No] to disable call waiting.
Headset TX gain (dB): Set to [0 dB].
Headset RX gain (dB): Set to [0 dB].
Click [Update] to save changes made.
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