File Exchange does not have On and Off buttons, but you can still turn it on and off by using AppleScript. Here are scripts that enable and disable the PC file system.
To enable the PC file system, enter the following in Script Editor and run it.
tell application "File Exchange"
set PC file system enabled to true
end tell
To disable the PC file system, enter the following in Script Editor and run it.
tell application "File Exchange"
set PC file system enabled to false
end tell
If you need to disable File Exchange often, you may want to save the two scripts as applications.