Apple Logic Express 9 - Manual (Page 289)

As you do so, the (send amount) value is shown on the Send slot.
The send amount, when set to 100%, routes the entire signal from the audio or instrument
channel strip to the aux channel. (See
Using Pre Fader, Post Fader, and Post Pan Sends .)
3 Insert the effect plug-ins you want, and set the required level, pan, and output settings
for the destination aux channel strip.
To remove a send
µ
Click an active Send slot, then choose No Send from the menu.
To bypass a send
µ
Option-click the Send slot.
The Send slot background turns gray.
To normalize (reset) the send level
µ
Option-click the Send knob.
This action resets the send level to 0 dB.
Using Pre Fader, Post Fader, and Post Pan Sends
Sends can be positioned either before (pre) or after (post) the (source) channel strip level
fader.
289 Chapter 10 Working with Instruments and Effects