LG GD570 - Manual (Page 72)

Call Functions
70 LG GD570 | User Guide
Muting or Sending Key Tones
During a call, these options allow you to turn the
key tones off or on. If the Disable Tones option is
selected, your phone does not transmit the DTMF
(Dual Tone Multi-Frequency) tones when keys are
pressed.
To turn the DTMF key tones off or on.
During a call, press the 1 Options soft key, and
select Disable Tones to turn the key tones off.
To turn them back on, press the 2 Options soft key,
and select Send Tones to turn the key tones on.
Note: To communicate with answering machines
or computerized telephone systems, Key Tones
must be set to On.