LG C3100 User Manual page 114

If Call Waiting is on, you can put the first call on hold and answer
the second, by pressing S [Send] or by selecting < [Answer], then
Hold & Answer.
You can end the current call and answer the waiting call by
selecting < [Menu], then End & Answer.
1-5 Muting the Microphone
You can mute the microphone during a call by pressing the <
[Options] key then selecting Mute. The handset can be unmuted by
pressing the < [Unmute].
When the handset is muted, the caller cannot hear you, but you can
still hear them.
1-6 Switching DTMF Tones on During a Call
To turn DTMF tones on during a call, for example, to allow your
handset to make use of an automated switchboard, select <
[Options], then DTMF On. DTMF tones can be turned off the same
way.
1-7 Calling up Messages and SIM Tool kit main menu
The Messages and SIM Tool kit main menu options can be reached
from the in-call menu by selecting < [Options]. SIM Tool kit menu
is shown only when SIM in the handset supports SIM Tool kit
service.
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