Yaesu FT-7900R Operating Manual page 21

. LOCK Switch
This switch locks out the Microphone's buttons (except for the PTT switch).
[ UP ] / [ DWN ] Button
Press (or hold in) either of these buttons to tune (or scan up or down) the operating
frequency or through the memory channels. In many ways, these buttons emulate the
function of the (rotary) DIAL knob.
Notice: If you change the microphone from the MH-48
vice versa, change the setting of Menu #22 (MIC
FT-7900R O
PERATING
MH-42
M
ANUAL
M
B6JS
ICROPHONE
to the MH-42
A6J
MIC). See page 73 for details.
MIC MIC
MIC
or
B6JS
19