Yaesu FT-991A Operating Manual page 75

Transmitter Convenience Features
VOX ( SSB/AM/FM Modes:
5 ) When you are satisfied with the setting, touch
[ ENTER ] on the TFT LCD display to save the
new setting.
6 ) Press the MENU ( SETUP ) button or touch
[ BACK ] on the LCD to exit to normal operation.
 The Anti-Trip setting adjusts the level of negative re-
ceiver audio feedback to the microphone, to prevent
receiver audio from activating the transmitter ( via
the microphone ) . This setting can also be adjusted
via Menu item "145 ANTI VOX GAIN".
 VOX operation may be engaged on either Voice
modes ( SSB/AM/FM ) or on AFSK-based Data
modes. Use Menu item "142 VOX SELECT" ( the se-
lections are "MIC" and "DATA" ) .
FT- 991 Operating Manual
Automatic TX/RX Switching using Voice Control
)
Page 73