PocketWizard CM-N3-P Canon N3 Motor Drive Cord, Pre-Releaseable Features:
For remotely triggering the electronic shutter release of Canon cameras equipped with an N3 remote terminal, through a pre-trigger switch.
This cable contains a pre-trigger switch. When enabled, the camera behaves as if the camera's shutter release button were held half-pressed continuously. This makes the camera respond more quickly and consistently, but also consumes the camera's batteries much more quickly. When disabled, this cable functions identically to the CM-N3.