Lucent Technologies Voice Terminal 8403 User Manual page 7

Volume control button only For adjusting the volume of the following:
The one-way speaker when a call is in progress using the speaker
The handset receiver level while a call is in progress using the
handset
The tone ringer when the speaker is off and either the handset is
inactive or the tone ringer is active
Note: When the speaker is active, the ringer volume is
automatically reduced to a low setting. The volume is restored when
the speaker is turned off.
Remember: The Volume control button on your voice terminal
does not control the volume level of adjunct equipment.
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