The majority of the bulk is being taken up by the programming module. The lock itself (the ground-level stuff to the right if you're facing the programming levers) is actually quite compact.
The levers behind the torches filter the input. When a lever is activated, it locks the torch in the "off" position. When a lever is deactivated, it allows input from the buttons to change the state of the torch.
The majority of the bulk is being taken up by the programming module. The lock itself (the ground-level stuff to the right if you're facing the programming levers) is actually quite compact.