Anritsu MG3641A - Manual (Page 55)

SECTION 4 OPERATING INSTRUCTIONS
4.5.5 Switching the Output Signal On/Off
You can switch on and off the output signal that goes through the output connector by pressing the [RF Off/On] key.
When the output signal is cut off, the lamp of the [RF Off/On] key will light up.
An output level you set with the output signal cut off will become effective the next time you switch on the output
signal.
[RF Off/On] key
MG3641A/MG3642A front panel