These cords are used to trigger your camera connected to your Pocket Wizard Receiver.
 

About Pre-trigger cords ( No Switch )  
Pictures # 1 and # 2 ( above )
The Pre-trigger cord keeps the camera "awake" ready  for the shot. Same mode as pressing the shutter half way down. The only way to view your pictures is to unplug the cord from the camera.. Depending on the way you shoot you may or may not need the switch. The camera will remain awake and use up more power.
For Canon   $ 95.00 ea.       For Nikon $ 95.00 ea.

About Pre-trigger cords ( with Switch )  
Pictures # 3 and # 4 ( above )
This cord also keeps the camera "awake" ready  for the shot. When you want to view the photos, Switch off the pretrigger and the camera operates normally as if no cord were in the camera. You can now view and edit your pictures normally. Turn the switch back on, the camera focuses. You are ready for your next photo session. Turn switch off, camera is able to sleep saving power. Also less ware and tare on camera and cord from constant unplugging.
For Canon   $ 125.00 ea.       For Nikon $ 125.00 ea.