On the ELD there are two locations on the lower-right-front (holding it in your hand for use...) for an activator "button," or cable. The button-or-cable activates the camera for both film and digital backs. You choose which location to insert the button-or-cable, for digital or film. Always carry an extra button....and an extra cable!
The digital sync cord attached to the lens activates the digital back.
"Wake-up" needs vary, depending on the digital back. I shoot with an ELD+Leaf Aptus-65. No "wake-up" needed...except for the photographer! If I accidentally trip the shutter before the back is "awake," the exposure sequence is interrupted, and I just take another shot.
Although there are some electrical contact-points on the rear of the ELD body, I've not found they have any bearing on the operation of my back. I assume they function for other backs.
Enjoy!