This is a nice small joystick to add some control to your modular. The joystick is acting as an attenue-inverter. At center position is zero. Swinging the joystick side to side gives + or -. There are two attenue-inverters, one for each axis. When nothing is patched into the 'input' jack, the joystick is using an internal reference voltage (7v). You can use that to control a fitler module for example.When you patch a vco or lfo into the input jack you can add some fm to another external vco and have control over the FM with the Joystick.The joystick also has a push button. The gate out jack allow you to trigger your other modules that don't have manual trigger control.