Apple Logic Pro 9 - Manual (Page 1105)

For controllers, the MSB uses the Input definition controller number, and the LSB uses
the controller number 32 or higher. This conforms to the MIDI standard for sending
14-bit controller data.
When this filter setting is chosen, the fader’s Range can be set to a maximum value of
16,383. A fader value of 8192 represents no pitch bend.
• Feedback: When the Feedback parameter is turned off (unselected), the fader
automatically prevents feedback loops resulting from circular cabling. (The fader
remembers when a specific MIDI event has passed through it and will not allow it to
pass through again.)
In some instances, you may want to enable feedback—to allow a MIDI event to change
a cable switcher’s position after it has passed through the switch, for example. Selecting
the Feedback checkbox will allow this.
Vector Fader
Vector faders function like joysticks. They can be moved in two dimensions: up and down
and left and right. Each dimension generates its own MIDI events, so each time you
change the position of the crosshair with the mouse, two MIDI events are sent.
Most faders have Input and Output definitions, which determine the MIDI events sent by
the fader (Output), and those it reacts to (Input). (See
Fader Functions: Range, Value As .)
The vector style fader replaces these with Vert and Horz definitions, which determine the
MIDI events that correspond to vertical and horizontal motion. If corresponding MIDI
events are received by the vector style fader, its crosshair display updates accordingly.
1105 Chapter 37 Environment Objects Reference