How do I turn off Fixed Level inputs on my 851A?

To disable Fixed Level inputs please follow the steps below:

1. Select the input you would like to adjust.
2. Hold down the 'menu' button on the front panel to go into the 'config menu'.
3. Navigate to the 'fixed input' menu and set turn the volume knob all the way to minimum. 
4. When minimum volume is reached, the fixed input should click to 'off' and the fixed input should now be disabled.