Press                  . 
  The MOD Output BNC will output 100Hz sine wave. 
In  addition,  you  can  use                                and  the  Rotate  Knob  to  modify  the 
value you need. 
 
6.12 Setup of FM Modulation 
The  FM  modulation  function  offers  internal  sine,  square,  and  triangle  (Ramp) 
signals.  Besides,  you  can  select  the  modulation  signal  from  external 
(Modulation/Trigger Input BNC). 
 Set the main output function by pressing                button. 
 Set the main output Amplitude by pressing                button and number keys. 
 Set the main output frequency by pressing                button and number keys. 
 Select the modulation mode by pressing                +                buttons. 
 Select the modulation signal source by pressing                +                  buttons. 
 Press                to set up modulation RATE value (Range 0.01Hz ~ 10kHz). 
To select the modulation signal by pressing                  and                buttons. 
    GFG-3015 offers sine, square, and triangle (ramp) signals for internal 
modulation.