[weegee]

That diagram is incomplete. It doesn't show how the wires loop throught the collar itself (see the red, yellow, and green)

[Vigilantcitizen]

"That diagram is incomplete. It doesn't show how the wires loop throught the collar itself (see the red, yellow, and green)."

Since the explosive was located right up under the lock box, the only reason to thread the wires through the collar itself is to keep the device from being cut off with some sort of torch.