Pocketwizard CM-E3-P

Pre-Trigger Remote Cable, for connecting a Plus II or MultiMAX with no ACC port to a Canon E3 or sub miniphone (3/32" or 2.5 mm) remote shutter release terminal through a pre-trigger switch.

Cable length: 3' (91.5 cm)

From: 1/8" (3.5 mm) mono miniphone
Through pre-trigger switch
To: Canon E3 remote shutter release terminal

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-E3

This Pre-Trigger (CM-E3–P) cable works with most PocketWizard radios. This pre-trigger cable has a switch that allows you to toggle half-press on or off at the camera position, but not remotely.